RESUMO
The major ampullate Spidroin 1 (MaSp1) is the main protein of the dragline spider silk. The C-terminal (CT) domain of MaSp1 is crucial for the self-assembly into fibers but the details of how it contributes to the fiber formation remain unsolved. Here we exploit the fact that the CT domain can form silk-like fibers by itself to gain knowledge about this transition. Structural investigations of fibers from recombinantly produced CT domain from E. australis MaSp1 reveal an α-helix to ß-sheet transition upon fiber formation and highlight the helix No4 segment as most likely to initiate the structural conversion. This prediction is corroborated by the finding that a peptide corresponding to helix No4 has the ability of pH-induced conversion into ß-sheets and self-assembly into nanofibrils. Our results provide structural information about the CT domain in fiber form and clues about its role in triggering the structural conversion of spidroins during fiber assembly.
Assuntos
Fibroínas , Aranhas , Fibroínas/química , Fibroínas/metabolismo , Animais , Aranhas/metabolismo , Seda/química , Seda/metabolismo , Domínios Proteicos , Sequência de Aminoácidos , Conformação Proteica em Folha beta , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Proteínas Recombinantes/genética , Concentração de Íons de Hidrogênio , Conformação Proteica em alfa-Hélice , Estrutura Secundária de ProteínaRESUMO
SUMMARY: Analysis of conservation of gene neighbourhoods over different evolutionary levels is important for understanding operon and gene cluster evolution, and predicting functional associations. Our tool FlaGs (standing for Flanking Genes) takes a list of NCBI protein accessions as input, clusters neighbourhood-encoded proteins into homologous groups using sensitive sequence searching, and outputs a graphical visualization of the gene neighbourhood and its conservation, along with a phylogenetic tree annotated with flanking gene conservation. FlaGs has demonstrated utility for molecular evolutionary analysis, having uncovered a new toxin-antitoxin system in prokaryotes and bacteriophages. The web tool version of FlaGs (webFlaGs) can optionally include a BLASTP search against a reduced RefSeq database to generate an input accession list and analyse neighbourhood conservation within the same run. AVAILABILITY AND IMPLEMENTATION: FlaGs can be downloaded from https://github.com/GCA-VH-lab/FlaGs or run online at http://www.webflags.se/. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.