NMR structure of protein YvyC from Bacillus subtilis reveals unexpected structural similarity between two PFAM families

Abstract

109-residue protein YvyC (MW=13 kDa) from B. subtilis (gi|580862, SwissProt/TrEMBL ID YVYC_BACSU, accession number {type:entrez-protein,attrs:{text:P39737,term_id:732320,term_text:P39737}}P39737) was selected as a target of the Protein Structure Initiative 2 and assigned to the Northeast Structural Genomics consortium (NESG; http://www.nesg.org) for structure determination (NESG Target ID SR482). YvyC belongs to the Pfam1 protein family FlaG (PF03646) and is required for proper assembly of bacterial flagella. The FlaG family contains 215 members (for sequence alignment of the FlaG family seeds see Fig. S1 in the Supporting Information). The NMR structure of YvyC presented here is the first atomic resolution structure available for this family. Self-assembly of bacterial flagella has been studied extensively in recent decades and comprehensive reviews are available.2-4 The gene encoding YvyC is a part of the fliD operon comprising the genes yvyC, fliD, fliS and fliT.5 This operon is located immediately downstream of the gene hag (also called fliC) encoding flagellin – the major protein required for assembly of the flagellar filaments. During filament elongation, flagellin monomers are exported through the central channel of a flagellum and oligomerize at its distal end.2,4 FliD (also named ‘hook-associated protein 2’, or HAP26) forms a pentameric cap at the distal end of a flagellum and is essential for oligomerization of flagellin.2,4,7 FliS and FliT serve as flagellin-specific8 and FliD-specific9,10 chaperones, respectively. It was demonstrated that mutations in yvyC gene orthologs in P. fluorescens (flaG) and V. anguillarum (ORF3) lead to phenotypes with unusually long filaments,11,12 but the specific role of YvyC remains unknown.