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Conservation of silk genes in Trichoptera and Lepidoptera.

Yonemura N, Mita K, Tamura T, Sehnal F - J. Mol. Evol. (2009)

Bottom Line: They are extremely uniform in R. obliterata.The trichopteran H-fibroins further contain charged amphiphilic motifs but lack the strings of alanines or alanine-glycine dipeptides that are typical lepidopteran motifs.On the other hand, sequences composed of a motif similar to ERIVAPTVITR surrounded by the (SX)(4-6) strings and modifications of the GRRGWGRRG motif occur in Trichoptera and not in Lepidoptera.

View Article: PubMed Central - PubMed

Affiliation: National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, 305-8634, Japan.

ABSTRACT
Larvae of the sister orders Trichoptera and Lepidoptera are characterized by silk secretion from a pair of labial glands. In both orders the silk filament consists of heavy (H)- and light (L)-chain fibroins and in Lepidoptera it also includes a P25 glycoprotein. The L-fibroin and H-fibroin genes of Rhyacophila obliterata and Hydropsyche angustipennis caddisflies have exon/intron structuring (seven exons in L-fibroin and two in H-fibroin) similar to that in their counterparts in Lepidoptera. Fibroin cDNAs are also known in Limnephilus decipiens, representing the third caddisfly suborder. Amino acid sequences of deduced L-fibroin proteins and of the terminal H-fibroin regions are about 50% identical among the three caddisfly species but their similarity to lepidopteran fibroins is <25%. Positions of some residues are conserved, including cysteines that were shown to link the L-fibroin and H-fibroin by a disulfide bridge in Lepidoptera. The long internal part of H-fibroins is composed of short motifs arranged in species-specific repeats. They are extremely uniform in R. obliterata. Motifs (SX)(n), GGX, and GPGXX occur in both Trichoptera and Lepidoptera. The trichopteran H-fibroins further contain charged amphiphilic motifs but lack the strings of alanines or alanine-glycine dipeptides that are typical lepidopteran motifs. On the other hand, sequences composed of a motif similar to ERIVAPTVITR surrounded by the (SX)(4-6) strings and modifications of the GRRGWGRRG motif occur in Trichoptera and not in Lepidoptera.

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Silk proteins of Rhyacophila obliterata separated by polyacrylamide electrophoresis from silk fibers used to construct shelters for pupation (a) and from dope collected from the silk gland lumen (b). The arrow in A indicates the fraction proven to be L-fibroin. Note that proteins of similar size occur also in the silk dope
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Fig2: Silk proteins of Rhyacophila obliterata separated by polyacrylamide electrophoresis from silk fibers used to construct shelters for pupation (a) and from dope collected from the silk gland lumen (b). The arrow in A indicates the fraction proven to be L-fibroin. Note that proteins of similar size occur also in the silk dope

Mentions: N-terminal sequencing of a 26-kDa protein extracted from the silk used to glue sand grains into protective domes (Fig. 2a) yielded the sequence AIQPALIEAT, which matched residues 20–29 of the deduced L-fibroin sequence. Analyzed protein was obviously secreted L-fibroin; the first 19 residues of L-fibroin deduced from the cDNA represented the signal peptide. A 26-kDa fraction was also detected among proteins extracted from the silk gland lumen of larvae several weeks before pupation (Fig. 2b).Fig. 2


Conservation of silk genes in Trichoptera and Lepidoptera.

Yonemura N, Mita K, Tamura T, Sehnal F - J. Mol. Evol. (2009)

Silk proteins of Rhyacophila obliterata separated by polyacrylamide electrophoresis from silk fibers used to construct shelters for pupation (a) and from dope collected from the silk gland lumen (b). The arrow in A indicates the fraction proven to be L-fibroin. Note that proteins of similar size occur also in the silk dope
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2691926&req=5

Fig2: Silk proteins of Rhyacophila obliterata separated by polyacrylamide electrophoresis from silk fibers used to construct shelters for pupation (a) and from dope collected from the silk gland lumen (b). The arrow in A indicates the fraction proven to be L-fibroin. Note that proteins of similar size occur also in the silk dope
Mentions: N-terminal sequencing of a 26-kDa protein extracted from the silk used to glue sand grains into protective domes (Fig. 2a) yielded the sequence AIQPALIEAT, which matched residues 20–29 of the deduced L-fibroin sequence. Analyzed protein was obviously secreted L-fibroin; the first 19 residues of L-fibroin deduced from the cDNA represented the signal peptide. A 26-kDa fraction was also detected among proteins extracted from the silk gland lumen of larvae several weeks before pupation (Fig. 2b).Fig. 2

Bottom Line: They are extremely uniform in R. obliterata.The trichopteran H-fibroins further contain charged amphiphilic motifs but lack the strings of alanines or alanine-glycine dipeptides that are typical lepidopteran motifs.On the other hand, sequences composed of a motif similar to ERIVAPTVITR surrounded by the (SX)(4-6) strings and modifications of the GRRGWGRRG motif occur in Trichoptera and not in Lepidoptera.

View Article: PubMed Central - PubMed

Affiliation: National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, 305-8634, Japan.

ABSTRACT
Larvae of the sister orders Trichoptera and Lepidoptera are characterized by silk secretion from a pair of labial glands. In both orders the silk filament consists of heavy (H)- and light (L)-chain fibroins and in Lepidoptera it also includes a P25 glycoprotein. The L-fibroin and H-fibroin genes of Rhyacophila obliterata and Hydropsyche angustipennis caddisflies have exon/intron structuring (seven exons in L-fibroin and two in H-fibroin) similar to that in their counterparts in Lepidoptera. Fibroin cDNAs are also known in Limnephilus decipiens, representing the third caddisfly suborder. Amino acid sequences of deduced L-fibroin proteins and of the terminal H-fibroin regions are about 50% identical among the three caddisfly species but their similarity to lepidopteran fibroins is <25%. Positions of some residues are conserved, including cysteines that were shown to link the L-fibroin and H-fibroin by a disulfide bridge in Lepidoptera. The long internal part of H-fibroins is composed of short motifs arranged in species-specific repeats. They are extremely uniform in R. obliterata. Motifs (SX)(n), GGX, and GPGXX occur in both Trichoptera and Lepidoptera. The trichopteran H-fibroins further contain charged amphiphilic motifs but lack the strings of alanines or alanine-glycine dipeptides that are typical lepidopteran motifs. On the other hand, sequences composed of a motif similar to ERIVAPTVITR surrounded by the (SX)(4-6) strings and modifications of the GRRGWGRRG motif occur in Trichoptera and not in Lepidoptera.

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