Spider silk research has largely focused on spidroins, proteins that are the primary components of spider silk fibers. Although a number of spidroins have been characterized, other types of proteins associated with silk synthesis are virtually unknown. Previous analyses of tissue-specific RNA-seq libraries identified 647 predicted genes that were differentially expressed in silk glands of the Western black widow, Latrodectus hesperus. Only ∼5% of these silk-gland specific transcripts (SSTs) encode spidroins; although the remaining predicted genes presumably encode other proteins associated with silk production, this is mostly unverified. Here, we used proteomic analysis of multiple silk glands and dragline silk fiber to investigate the translation of the differentially expressed genes. We find 48 proteins encoded by the differentially expressed transcripts in L. hesperus major ampullate, minor ampullate, and tubuliform silk glands and detect 17 SST encoded proteins in major ampullate silk fibers. The observed proteins includeknown silk-related proteins, but most are uncharacterized, with noannotation. These unannotated proteins likely include novel silk-associatedproteins. Major and minor ampullate glands have the highest overlapof identified proteins, consistent with their shared, distinctiveampullate shape and the overlapping functions of major and minor ampullatesilks. Our study substantiates and prioritizes predictions from differentialexpression analysis of spider silk gland transcriptomes.
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