Highly repetitive structure and its organization of the silk fibroin gene

Mita, Kazuei; Ichimura, Sachiko; James, Tharappel C.

doi:10.1007/bf00175878

Cited by 226 publications

(183 citation statements)

References 40 publications

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“…This is likely to reduce the high degree of secondary structure of the transcript (Mita et al, 1988;Hinman and Lewis, 1992). (At least this has been observed in the silkworm where stretches of G and C are thought to create recombination hotspots, something which could destabilise the genes [Mita et al, 1994].) When MaSp1 sequences from different individuals are compared substantial allelic variation is displayed by the gene; this could be a result from replication slippage and unequal crossing-over.…”

Section: The Silk; Genes and Primary Structure Of The Proteinsmentioning

confidence: 99%

Spider Silk Proteins – Mechanical Property and Gene Sequence

et al. 2005

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-Spiders spin up to seven different types of silk and each type possesses different mechanical properties. The reports on base sequences of spider silk protein genes have gained importance as the mechanical properties of silk fibers have been revealed. This review aims to link recent molecular data, often translated into amino acid sequences and predicted three dimensional structural motifs, to known mechanical properties.

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Section: The Silk; Genes and Primary Structure Of The Proteinsmentioning

confidence: 99%

Spider Silk Proteins – Mechanical Property and Gene Sequence

et al. 2005

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“…About 75% of all serine residues occur within the sequence of the repetitive region (65), which forms crystalline domains. It was also found that ϳ75% of the serine residues in fibroin interact with carbonyl groups on adjacent chains to form intermolecular hydrogen-bonding networks in the fibroin fiber (66).…”

Section: Construction Of Recombinant Expression Plasmid Pet21a(ϩ)-srcn-mentioning

confidence: 99%

Cloning, Expression, and Assembly of Sericin-like Protein

Huang

Valluzzi

Bini

et al. 2003

Journal of Biological Chemistry

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Recombinant sericin proteins of different molecular masses (17.4, 31.9, and 46.5 kDa), based on the 38-amino acid repetitive motif of native sericin, were cloned, expressed, and purified. The recombinant sericin self-assembled during dialysis (starting concentration of 2.5 mg/ml) forming twisted fibers. Circular dichroism and Fourier transform infrared spectroscopy studies demonstrated protein conformational transitions occurred from random coil to ␤-sheets during the dialysis. Congo red-stained recombinant sericin fibrils exhibited applegreen birefringence, indicating long-range order in the array of ␤-sheets. Biosynthetic sericin has a high content of polar amino acids (e.g. Silk of Bombyx mori is composed of two kinds of proteins: the fibroin which is synthesized in the posterior silk gland and the sericins produced by the middle silk gland. The sericins bind two fibroin fibers together in the anterior region of the gland as the fibers are spun to form the cocoon. Sericins represent a family of proteins whose molecular mass ranges from 20 to 310 kDa (2, 3) and are characterized by an unusually high serine content, 38.1 mol % (4). Sericins are soluble in hot water, which makes it possible to degum the silk fibroin threads.Two genes encode sericins, Ser1 and Ser2 (5-8). The different molecular weight sericins are the products of different splicing events at the transcript level. Some conformation studies with sericins from the silk gland of B. mori or regenerated sericin from B. mori cocoons suggested random coil with some ␤ structure (9, 10). However, the samples used in these studies were mixtures of the various native sericin proteins, therefore the structure of the individual proteins is unknown and the contribution of specific sequences toward secondary structure is not confirmed. Sericin model peptides such as poly(L-serine) (11-16), poly(O-benzyl-L-serine) (12), and poly(O-acetyl-L-serine) (13,14) were synthesized for structural feature characterization. The ability of poly(L-serine) to fold into a ␤ conformation depended on molecular weight. Low molecular weight poly(L-serine) (molecular weight 650) was soluble and adopted a random coil conformation in aqueous solution, whereas high molecular weight poly(L-serine) (molecular weight 105,000) formed ␤-sheets and was insoluble in water (11). However, homopolypeptides like poly(L-serine) do not match native sericin in terms of amino acid composition, sequence, and molecular weight. Therefore, to better understand sericin structure, interactions between sericin and fibroin, and the biological relevance of sericin in fiber structure, high molecular weight pure sericin-like proteins are required.Sericin 1 encoded by Ser 1 consists of 70 repeats of the 38-amino acid motif (5): SSTGSSSNTDSNSNSVGSSTS-GGSSTYGYSSNSRDGSV. The molecular mass of sericin 1 proteins is 76 -284 kDa. The 38-amino acid repeat motif exhibits a high content of hydrophilic amino acids: 44.7% serine, 10.5% threonine, and 7.9% tyrosine, very close to the average amino acid composition of serici...

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“…Assembly of 28 S rRNA Sequence-The cDNA library including many clones for various sites of rRNA was prepared using total RNAs from the fat bodies of fifth-instar larvae of B. mori as described previously (36), except that pUC18 was used as vector instead of M13mp18. Sequencing of the cDNAs was carried out in an automated DNA sequencer (Models 373S and 377, Applied Biosystems, Inc.).…”

Section: Methodsmentioning

confidence: 99%

A Covariant Change of the Two Highly Conserved Bases in the GTPase-associated Center of 28 S rRNA in Silkworms and Other Moths

Uchiumi

Nomura

Shimizu

et al. 2000

Journal of Biological Chemistry

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The GTPase-associated center in 23/28 S rRNA is one of the most conserved functional domains throughout all organisms. We detected a unique sequence of this domain in Bombyx mori species in which the bases at positions 1094 and 1098 (numbering from Escherichia coli 23 S rRNA) are C and G instead of the otherwise universally conserved bases U and A, respectively. These changes were also observed in four other species of moths, but not in organisms other than the moths. Characteristics of the B. mori rRNA domain were investigated by native polyacrylamide gel electrophoresis using RNA fragments containing residues 1030 -1128. Although two bands of protein-free RNA appeared on gel, they shifted to a single band when bound to Bombyx ribosomal proteins Bm-L12 and Bm-P complex, equivalent to E. coli L11 and L8, respectively. Bombyx RNA showed lower binding capacity than rat RNA for the ribosomal proteins and anti-28 S autoantibody, specific for a folded structure of the eukaryotic GTPase-associated domain. When the C 1094 /G 1098 bases in Bombyx RNA were replaced by the conserved U/A bases, the proteinfree RNA migrated as a single band, and the complex formation with Bm-L12, Bm-P complex, and anti-28 S autoantibody was comparable to that of rat RNA. The results suggest that the GTPase-associated domain of moth-type insects has a labile structural feature that is caused by an unusual covariant change of the U 1094 /A 1098 bases to C/G.

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Highly repetitive structure and its organization of the silk fibroin gene

Cited by 226 publications

References 40 publications

Spider Silk Proteins – Mechanical Property and Gene Sequence

Spider Silk Proteins – Mechanical Property and Gene Sequence

Cloning, Expression, and Assembly of Sericin-like Protein

A Covariant Change of the Two Highly Conserved Bases in the GTPase-associated Center of 28 S rRNA in Silkworms and Other Moths

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