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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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Kyte-Doolittle hydropathy plot of the N- and C-terminal regions of R. obliterata H-fibroin. The first 150 and last 75 residues make up the nonrepetitive ends, while the major central part is composed of repeats
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Fig7: Kyte-Doolittle hydropathy plot of the N- and C-terminal regions of R. obliterata H-fibroin. The first 150 and last 75 residues make up the nonrepetitive ends, while the major central part is composed of repeats

Mentions: Bini et al. (2004) suggested that proteins forming water-resistant silk filament must include hydrophilic terminal domains flanking a very long central portion constructed from the hydrophobic blocks alternating with short hydrophilic regions. The strong predominance of hydrophobicity in the major polymerizing part was regarded as essential for water exclusion during β-crystallite formation, while the hydrophilic terminal regions allowed fibroin hydration during storage in the silk gland lumen. These rules may apply to aerial silks spun by caterpillars or spiders but are contradicted by the content and distribution of hydrophilic amino acid residues in the repetitive domain of caddisfly H-fibroins. The amphiphilic plot of R. obliterata H-fibroin reveals a predominance of hydrophilic regions (Fig. 7), very similar to the situation described for H. angustipennis and L. decipiens (Yonemura et al. 2006) and different from that in most Lepidoptera (Sehnal and Žurovec 2004).Fig. 7


Conservation of silk genes in Trichoptera and Lepidoptera.

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

Kyte-Doolittle hydropathy plot of the N- and C-terminal regions of R. obliterata H-fibroin. The first 150 and last 75 residues make up the nonrepetitive ends, while the major central part is composed of repeats
© Copyright Policy
Related In: Results  -  Collection

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

Fig7: Kyte-Doolittle hydropathy plot of the N- and C-terminal regions of R. obliterata H-fibroin. The first 150 and last 75 residues make up the nonrepetitive ends, while the major central part is composed of repeats
Mentions: Bini et al. (2004) suggested that proteins forming water-resistant silk filament must include hydrophilic terminal domains flanking a very long central portion constructed from the hydrophobic blocks alternating with short hydrophilic regions. The strong predominance of hydrophobicity in the major polymerizing part was regarded as essential for water exclusion during β-crystallite formation, while the hydrophilic terminal regions allowed fibroin hydration during storage in the silk gland lumen. These rules may apply to aerial silks spun by caterpillars or spiders but are contradicted by the content and distribution of hydrophilic amino acid residues in the repetitive domain of caddisfly H-fibroins. The amphiphilic plot of R. obliterata H-fibroin reveals a predominance of hydrophilic regions (Fig. 7), very similar to the situation described for H. angustipennis and L. decipiens (Yonemura et al. 2006) and different from that in most Lepidoptera (Sehnal and Žurovec 2004).Fig. 7

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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