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Publication Abstract from PubMed

Archaea employ the archaellum, a type IV pilus-like nanomachine, for swimming motility. In the crenarchaeon Sulfolobus acidocaldarius, the archaellum consists of seven proteins: FlaB/X/G/F/H/I/J. FlaF is conserved and essential for archaellum assembly but no FlaF structures exist. Here, we truncated the FlaF N terminus and solved 1.5-A and 1.65-A resolution crystal structures of this monotopic membrane protein. Structures revealed an N-terminal alpha-helix and an eight-strand beta-sandwich, immunoglobulin-like fold with striking similarity to S-layer proteins. Crystal structures, X-ray scattering, and mutational analyses suggest dimer assembly is needed for in vivo function. The sole cell envelope component of S. acidocaldarius is a paracrystalline S-layer, and FlaF specifically bound to S-layer protein, suggesting that its interaction domain is located in the pseudoperiplasm with its N-terminal helix in the membrane. From these data, FlaF may act as the previously unknown archaellum stator protein that anchors the rotating archaellum to the archaeal cell envelope.

FlaF Is a beta-Sandwich Protein that Anchors the Archaellum in the Archaeal Cell Envelope by Binding the S-Layer Protein.,Banerjee A, Tsai CL, Chaudhury P, Tripp P, Arvai AS, Ishida JP, Tainer JA, Albers SV Structure. 2015 Apr 3. pii: S0969-2126(15)00079-9. doi:, 10.1016/j.str.2015.03.001. PMID:25865246^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.