Uno T, Nakada T, Okamaoto S, Nakamura M, Matsubara M, Imaishi H, Yamagata H, Kanamaru K, Takagi M.
Arch Insect Biochem Physiol. 2007 Oct;66(2):89-97.
The Rab family of small GTPases are key regulators of membrane trafficking. Partially purified Rab8 from Bombyx mori (BRab8) was phosphorylated by protein kinase C in mammalian cells in vitro. To determine which of the seven serines and four threonines are phosphorylated, we generated deletion and site-directed mutants of BRab8, inserted them in Escherichia coli, partially purified the encoded fusion proteins by affinity chromatography, and examined their phosphorylation by protein kinase C in vitro. We found that Ser-132 of BRab8 was specifically phosphorylated by protein kinase C. In addition, Western blotting using an antiserum against BRab8 and in-gel staining for phosphorylated proteins revealed that BRab8 is phosphorylated in vivo.
Shao YM, Dong K, Zhang CX.
BMC Genomics 2007, 8:324doi:10.1186/1471-216
Tomita M, Hino R, Ogawa S, Iizuka M, Adachi T, Shimizu K, Sotoshiro H, Yoshizato K. (Yoshizato Project, Cooperative Link of Unique Science and Technology for Economy Revitalization, Hiroshima Prefectural Institute of Industrial Science and Technology, 3-10-32 Kagamiyama, Higashihiroshima, Hiroshima, 739-0046, Japan.)
Transgenic Res. 2007 Aug;16(4):449-65. Epub 2007 Apr 6.
A silk thread of the silkworm, Bombyx mori, is composed of the insoluble inner fibroin and the hydrophilic outer sericin layer, which are synthesized in the posterior and middle silk gland (MSG), respectively. This study aimed to develop a novel sericin 1 gene (ser1) promoter-driven recombinant expression system using transgenic silkworms, in which recombinant proteins are synthesized in MSG and secreted into the sericin layer. To obtain a high level of gene expression, we tested whether a baculovirus-derived enhancer, hr3, and a trans-regulator, IE1, are capable of stimulating the transcriptional activity of the ser1 promoter, using a transient gene expression system. The results showed that hr3 and IE1 cooperatively increased the ser1 promoter activity more than 30-fold. Then, transgenic silkworms were generated which expressed the EGFP with the signal peptide in MSG under the control of the hr3-linked ser1 promoter and IE1 gene. The silkworms exclusively secreted the EGFP into the sericin layer of cocoons as predicted. The expressed EGFP was extractable from cocoons through a simple procedure with neutral pH buffer solution. The expression system developed in this study enables us to produce recombinant proteins in bulk that can be easily extracted and purified.
Ogawa S, Tomita M, Shimizu K, Yoshizato K.(Yoshizato Project, Cooperative Link of Unique Science and Technology for Economy Revitalization, Hiroshima Prefectural Institute of Industrial Science and Technology, 3-10-32 Kagamiyama, Higashihiroshima, Hiroshima 739-0046, Japan.)
J Biotechnol. 2007 Feb 20;128(3):531-44. Epub 2006 Nov 17.
In this study we produced germline transgenic silkworms that spin cocoons containing recombinant human serum albumin (rHSA) in the sericin layer. A piggyBac-based transformation vector was constructed that carried HSA cDNA driven by sericin-1 gene promoter, viral enhancer hr3, and gene encoding viral trans-activator IE1. Isolated silk glands were bombarded with the vector and transplanted into host larvae. Three days later, the transplants were immunohistochemically analyzed, which showed that middle silk gland (MSG) cells expressed rHSA and secreted it into the MSG lumen. Then, silkworm eggs were injected with the vector and developed to larvae. The obtained transgenic silkworms spun silk threads whose sericin layers contained rHSA at 3.0microg/mg of cocoons. Most (83%) of the rHSA in cocoons was extracted with phosphate buffered saline, which was then subjected to ammonium sulfate precipitation and affinity chromatography. Finally, we obtained 2.8mg of 99%-pure rHSA from 2g of cocoons. Measurements of circular dichroism spectra of rHSA, and equilibrium dissociation constants of rHSA to warfarin and naproxen indicated that rHSA was conformationally and functionally identical to natural plasma HSA. Germline transgenic silkworms will be useful for producing various recombinant proteins in the sericin layer of cocoons.
Guo XY, Guo TQ, Wang SP, Wang JY, Lu CD. (Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, PR China.)
Arch Virol. 2005 Jun;150(6):1151-60. Epub 2005 Feb 10.
To evaluate the possibility of establishing an in vivo baculovirus expression system in a silk gland specific secretory way, the recombinant Autographa californica nucleopolyhedrovirus (AcserpegfpDeltaEGT) carrying the reporter gene egfp downstream of silkworm ser1 promoter and signal peptide coding sequence was generated. The purified recombinant baculovirus AcserpegfpDeltaEGT was injected into the haemocoel of newly ecdysed 5thHendekl) instar silkworm larvae at the amount of 10(6) pfu per larva. At 5 days post injection, green fluorescence derived from EGFP could be observed with fluorescent microscope in only the silk gland but not other tissues after dissection of the silkworm. By making an opening on the silk gland wall, green fluorescence could be observed in the outflow of silk gland indicating the secretion of EGFP and the effectiveness of ser1 signal peptide. Western blotting assay confirmed that EGFP exists in the water-soluble part of cocoon silk too. We also established a simple protocol to purify EGFP from the secreted silk proteins.
Liu Y, Yu L, Guo X, Guo T, Wang S, Lu C. (College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou 310027, China.)
Biochem Biophys Res Commun. 2006 Mar 31;342(1):273-9. Epub 2006 Feb 6
The gene encoding sericin 1 (Ser1) of silkworm (Bombyx mori) is specifically expressed in the middle silk gland cells. To identify element involved in this transcription-dependent spatial restriction, truncation of the 5' terminal from the sericin 1 (Ser1) promoter is studied in vivo. A 209bp DNA sequence upstream of the transcriptional start site (-586 to -378) is found to be responsible for promoting tissue-specific transcription. Analysis of this 209bp region by overlapping deletion studies showed that a 25bp region (-500 to -476) suppresses
the ectopic expression of the Ser1 promoter. An unknown factor abundant in fat body nuclear extracts is shown to bind to this 25bp fragment. These results suggest that this 25bp region and the unknown factor are necessary for determining the tissue-specificity of the Ser1 promoter.
Li BC, Zhang SQ, Dan WB, Chen YQ, Cao P. (Jiangsu Province Key Laboratory for Molecular and Medical Biotechnology, Life Sciences College, Nanjing Normal University, Jiangsu, Nanjing, PR China.)
Biotechnol Lett. 2007 Jul;29(7):1031-6. Epub 2007 Mar 21.
The antibacterial peptide CM4 (ABP-CM4), isolated from Chinese Bombys mori, is a 35-residue cationic, amphipathic alpha-helical peptide that exhibits a broad range of antimicrobial activity. To explore a new approach for the expression of ABP-CM4 in E. coli, the gene ABP-CM4, obtained by recursive PCR (rPCR), was cloned into the vector pET32a to construct a fusion expression plasmid. The fusion protein Trx-CM4 was expressed in soluble form, purified by Ni(2+)-chelating chromatography, and cleaved by formic acid to release recombinant CM4. Purification of rCM4 was achieved by affinity chromatography and reverse-phase HPLC. The purified of recombinant peptide showed antimicrobial activities against E. coli K(12)D(31), Penicillium chrysogenum, Aspergillus niger and Gibberella saubinetii. According to the antimicrobial peptide database (http://aps.unmc.edu/AP/main.html), 116 peptides contain a Met residue, but only 5 peptides contain the AspPro site, indicating a broader application of formic acid than CNBr in cleaving fusion protein. The successful application to the expression of the ABP-CM4 indicates that the system is a low-cost, efficient way of producting milligram quantities of ABP-CM4 that is biologically active.
Li BC, Chen YQ, Liu P, Zhang SQ. (The Life Science School of Nanjing Normal University, Nanjing 210097. email@example.com)
Fen Zi Xi Bao Sheng Wu Xue Bao. 2007 Apr;40(2):98-102
[Article in Chinese] According to the amino acid sequence of CM4 and the bias for preferred condons of E. coli, the CM4-like gene was obtained by a recursive PCR (rPCR) strategy using two lapping oligonucleotides. The synthesized gene was coloned into the expression vector pET32(a) and transformed into E. coli BL21 (DE3). Recombinant CM4-like gene expression was driven by the T7 promoter on the vector upon addition of IPTG and high level of expression was achieved. The solube protein was purified by Ni-chelating agarose and treated with formic acid. After cleavege, the recombinant peptide was purified by another Ni(2+)-NTA-Agarose affinity chromatography and cation-exchange chromatography. Results of agarose diffuse assay and liquid turbidity analysis indicated that the recombinant peptide exhibited the antibacterial activity.
Damberger FF, Ishida Y, Leal WS, Wuthrich K.
J Mol Biol. 2007 Aug 17; [Epub ahead of print]
The NMR structure of the Antheraea polyphemus pheromone-binding protein 1 at pH 4.5, ApolPBP1(A), was determined at 20 degrees C. The structure consists of six alpha-helices, which are arranged in a globular fold that encapsulates a central helix alpha7 formed by the C-terminal polypeptide segment 131-142. The 3D arrangement of these helices is anchored by the three disulfide bonds 19-54, 50-108 and 97-117, which were identified by NMR. Superposition of the ApolPBP1(A) structure with the structure of the homologous pheromone-binding protein of Bombyx mori at pH 4.5, BmorPBP(A), yielded an rmsd of 1.7 A calculated for the backbone heavy-atoms N, C(alpha) and C' of residues 10-142. In contrast, the present ApolPBP1(A) structure is different from a recently proposed molecular model for a low-pH form of ApolPBP1 that does not contain the central helix alpha7. ApolPBP1 exhibits a pH-dependent transition between two different globular conformations in slow exchange on the NMR chemical shift timescale similar to BmorPBP, suggesting that the two proteins use the same mechanism of ligand binding and ejection. The extensive sequence homology observed for pheromone-binding proteins from moth species further implies that the previously proposed mechanism of ligand ejection involving the insertion of a C-terminal helix into the pheromone-binding site is a general feature of pheromone signaling in moths.
Tao W, Li M, Zhao C.(School of Material Engineering, Stem Cell Research Laboratory of Jiangsu Province, Suzhou University, Campus Box 64, No. 178 East Gan-Jiang Road, Suzhou 215021, China.)
Int J Biol Macromol. 2007 Apr 10;40(5):472-8. Epub 2006 Nov 24.
Antheraea pernyi silk fibroin fibers were dissolved by aqueous lithium thiocyanate to obtain regenerated A. pernyi silk fibroin solution. By means of circular dichroism, (13)C NMR and Raman spectroscopy, the molecular conformation of regenerated A. pernyi silk fibroin in aqueous solution was investigated. The relationship of environmental factors and sol-gel transformation behavior of regenerated A. pernyi silk fibroin was also studied. The molecular conformations of regenerated A. pernyi silk fibroin mainly were alpha-helix and random coil in solution. There also existed a little beta-sheet conformation. It was obviously different with Bombyx mori silk fibroin, whose molecular conformation in solution was only random coil but no alpha-helix existence. With the increase of temperature and solution concentration and with the decrease of solution pH value, the gelation velocity of regenerated A. pernyi silk fibroin solution increased. Especially, it showed that A. pernyi silk fibroin was more sensitive to temperature than B. mori silk fibroin during the sol-gel transformation. The velocity increased obviously when the temperature was above 30 degrees C. During the sol-gel transformation, the molecular conformation of regenerated A. pernyi silk fibroin changed from random coil to beta-sheet structure. The results of these studies provided important insight into the preparation of new biomaterials by silk fibroin protein.
Freddi G, Anghileri A, Sampaio S, Buchert J, Monti P, Taddei P. (Stazione Sperimentale per la Seta, via Giuseppe Colombo 83, Milano, Italy. firstname.lastname@example.org)
J Biotechnol. 2006 Sep 1;125(2):281-94. Epub 2006 Apr 18
The capability of mushroom tyrosinase to catalyze the oxidation of tyrosine residues of Bombyx mori silk fibroin was studied under heterogeneous reaction conditions, by using a series of silk substrates differing in surface and bulk morphology and structure, i.e. hydrated and insoluble gels, mechanically generated powder and fibre. Tyrosinase was able to oxidize 10-11% of the tyrosine residues of silk gels. The yield of the reaction was very low for the powder and undetectable for fibres. FT-Raman spectroscopy gave evidence of the oxidation reaction. New bands attributable to vibrations of oxidized tyrosine species (o-quinone) appeared, and the value of the I853/I829 intensity ratio of the tyrosine doublet changed following oxidation of tyrosine. The thermal behaviour of SF substrates was not affected by enzymatic oxidation. o-Quinones formed by tyrosinase onto gels and powder were able to undergo non-enzymatic coupling with chitosan. FT-IR and FT-Raman spectroscopy provided clear evidence of the formation of silk-chitosan bioconjugates under heterogeneous reaction conditions. Chitosan grafting caused a beta-sheet --> random coil conformational transition of silk fibroin and significant changes in the thermal behaviour. Chitosan grafting did not occur, or occurred at an undetectable level on silk fibres. The results reported in this study show the potential of the enzymatically initiated protein-polysaccharide grafting for the production of a new range of bio-based, environmentally friendly polymers.
Taddei P, Arosio C, Monti P, Tsukada M, Arai T, Freddi G.(Centro di Studio sulla Spettroscopia Raman, Dipartimento di Biochimica G. Moruzzi, Università di Bologna, via Belmeloro 8/2, Bologna 40126, Italy.)
Biomacromolecules. 2007 Apr;8(4):1200-8. Epub 2007 Mar 6.
Silk fabrics were treated with chlorosulphonic acid in pyridine for different times. The amount of sulfur bound to silk increased during the first 2 h of reaction and then reached a plateau. The amino acidic pattern of sulfated silk remained essentially unchanged for short reaction times (< or ="2"> or =2 h). Spectroscopic analyses performed by FT-IR and FT-Raman showed the appearance of new bands attributable to various vibrations of sulfated groups. The IR bands at 1049 and 1014 cm-1, due to organic sulfate salts, were particularly intense. Bands assigned to alkyl sulfates and sulfonamides appeared in the 1300-1180 cm-1 range. Organic covalent sulfates displayed a weak but distinct IR band at 1385 cm-1. Both IR and Raman spectra revealed that silk fibroin mainly bound sulfates through the hydroxyl groups of Ser and Tyr, while involvement of amines could not be proved. Changes observed in the amide I and II range indicated an increase of the degree of molecular disorder of sulfated silk. Accordingly, the I850/I830 intensity ratio between the two Tyr bands at 850-830 cm-1 increased from 1.41 to 1.52, indicating a more exposed state of Tyr residues in sulfated silk. TGA, DSC, and TG analyses showed that sulfated silk attained a higher thermal stability. A thermal transition attributable to sulfated silk fibroin fractions appeared at about 260 degrees C in the DSCthermograms.
Wang H, Zhang Y, Shao H, Hu X.(State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Material Science and Engineering, Donghua University, Shanghai 200051, PR China).
Int J Biol Macromol. 2005 Jul;36(1-2):66-70
The flow stability of silk fibroin (SF) aqueous solutions with different concentrations under different temperatures was investigated. It was found that the flow stability decreased quickly with the increase of solution concentration and temperature. X-ray diffraction, Fourier transform infrared (FTIR) and Raman spectroscopy analysis showed that silk fibroin in aqueous solution was mainly in random coil and alpha-helix conformation. However, it turned into alpha-helix and beta-sheet conformation after gelation, and both silk I and silk II crystalline structures appeared accordingly. The investigation implies that the original dilute regenerated SF aqueous solution should be stored under low temperature and concentrated just before spinning.
1. Development and evaluation of silk fibroin-based nerve grafts used for peripheral nerve regeneration.
Yang Y, Ding F, Wu J, Hu W, Liu W, Liu J, Gu X.
Biomaterials. 2007 Sep 18; [Epub ahead of print]
Slk fibroin (SF), derived from natural silk long used as a textile material, has recently become an important biomaterial for tissue engineering applications. We have previously reported on good in vitro biocompatibility of SF fibers with peripheral nerve tissues and cells. In the present study, we developed a novel biomimetic design of the SF-based nerve graft (SF graft) which was composed of a SF-nerve guidance conduit (NGC) inserted with oriented SF filaments. The SF-NGC prepared via well-established procedures exhibits an eggshell-like microstructure that is responsible for its superior mechanical and permeable properties beneficial to nerve regeneration. The SF graft was used for bridge implantation across a 10-mm long sciatic nerve defect in rats, and the outcome of peripheral nerve repair at 6 months post-implantation was evaluated by a combination of electrophysiological assessment, FluoroGold retrograde tracing and histological investigation. The examined functional and morphological parameters show that SF grafts could promote peripheral nerve regeneration with effects approaching those elicited by nerve autografts which are generally considered as the gold standard for treating large peripheral nerve defects, thus raising a potential possibility of using these newly developed nerve grafts as a promising alternative to nerve autografts.
Gobin AS, Rhea R, Newman RA, Mathur AB. (University of Texas MD Anderson Cancer Center, Laboratory of Reparative Biology and Bioengineering, Plastic Surgery, Houston, TX 72230, USA.)
Int J Nanomedicine. 2006;1(1):81-7
Many barriers to drug delivery into a tumor site require careful consideration when designing a new drug. In this study, the adhesive targeting and drug specificity of modified liposomal vesicles on human-scar-producing cells, keloid fibroblasts, were investigated. Keloids express abundant levels of mucopolysaccharides and receptor tyrosine kinase (RTK). In this report, the structural properties, drug release kinetics, and therapeutic availability of silk-fibroin-coated, emodin-loaded liposomes (SF-ELP), compared with uncoated, emodin-loaded liposomes (ELP), were investigated. SF-ELP had a highly organized lamellae structure, which contributed to 55% of the liposomal diameter. This modified liposomal structure decreased emodin release rates by changing the release kinetics from a swelling and diffusional process to a purely diffusional process, probably due to steric hindrance. SF-ELP also increased adhesion targeting to keloid fibroblasts. Increased retention of SF-ELP is most likely due to the interaction of the fibrous protein coating around the ELP with the pericellular molecules around the cell. SF-ELP also decreased survival rate of keloids that expressed high levels of RTK. These results demonstrated that SF-ELP enhanced emodin delivery by improved diffusion kinetics and specific cell targeting.
Wang X, Hu X, Daley A, Rabotyagova O, Cebe P, Kaplan DL. (Department of Biomedical Engineering, Tufts University, Medford, Massachusetts 02155, USA.)
J Control Release. 2007 Aug 28;121(3):190-9. Epub 2007 Jun 14
An all-aqueous, stepwise deposition process with silk fibroin protein for the assembly of nanoscale layered controlled release coatings was exploited. Model compounds, Rhodamine B, Even Blue and Azoalbumin, representing small molecule drugs and therapeutically relevant proteins were incorporated in the nanocoating process and their loading and release behavior was quantified. In addition, the structure and morphology of the coatings were characterized. Release studies in vitro showed that control of beta-sheet crystal content and the multilayer structure of the silk coatings correlated with the release properties of the incorporated compounds. In particular, higher crystallinity and a thicker silk capping layer suppressed the initial burst of release and prolonged the duration of release. These novel coatings and deposition approach provide a unique option to regulate structure and morphology, and thus release kinetics. The results also suggest these systems as a promising framework for surface engineering of biomaterials and medical devices to regulate the release of drugs, when considered with the all-aqueous process involved, the conformal nature of the coatings, the robust material properties of silk fibroin, and the degradability and biocompatibility of this family of protein.
Cheema SK, Gobin AS, Rhea R, Lopez-Berestein G, Newman RA, Mathur AB. (University of Texas M.D. Anderson Cancer Center, Departments of Biomedical Engineering and Plastic Surgery, Unit 602, P.O. Box 301402, Houston, TX 72230-1402, United States.)
Int J Pharm. 2007 Aug 16;341(1-2):221-9. Epub 2007 Apr 3.
The efficacy of a drug is dependent on its mode of delivery and its potency at the tumor site. In this study, the drug delivery and efficacy of silk fibroin coated liposomes (SF-ELP), encapsulating a receptor tyrosine kinase inhibitor, emodin, on Her2/neu over-expressing breast cancer cells, was investigated. This study demonstrates that SF-ELP was more efficacious in suppressing the growth of Her2/neu over-expressing breast cancer cells MDA-MB-453 and BT-474 as compared to uncoated emodin loaded liposomes (ELP). Reduced levels of phosphorylated Her2/neu correlated with growth inhibition observed in the MDA-MB-453 cells, treated with both ELP and SF-ELP. ELP treatment of MDA-MB-453 breast cancer cells resulted in inhibition of the PI3K pathway whereas SF-ELP treatment inhibited both the PI3K and MAPK pathways, which contributed to the enhanced growth inhibitory effects of Her2/neu over-expressing breast cancer cells. Coating of ELP with silk fibroin did not alter the target specificity of emodin, on the other hand the emodin efficacy was enhanced. Higher uptake of emodin delivered by SF-ELP lead to increased cell death as compared to emodin delivery via ELP. Silk fibroin coating around the liposome imparts an extra layer that emodin has to extravasate in order to release from the encapsulating liposome. This increases retention of the drug in the cell for a longer time and protects emodin from quick release and metabolism. Longer intracellular retention may lead to the longer availability of emodin for down-modulation of various Her2/neu pathways. This study demonstrates that silk fibroin coating enhanced emodin delivery in Her2/neu over-expressing breast cancer cells thereby increasing the overall efficacy of the drug.
Kimura T, Nakagawa K, Kubota H, Kojima Y, Goto Y, Yamagishi K, Oita S, Oikawa S, Miyazawa T. (Food & Biodynamic Chemistry Laboratory, Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555, Japan. email@example.com)
J. Agric. Food Chem., 55 (14), 5869 -5874, 2007. 10.1021