TY - JOUR
T1 - FlaF is a β-sandwich protein that anchors the archaellum in the archaeal cell envelope by binding the S-layer protein
AU - Banerjee, Ankan
AU - Tsai, Chi Lin
AU - Chaudhury, Paushali
AU - Tripp, Patrick
AU - Arvai, Andrew S.
AU - Ishida, Justin P.
AU - Tainer, John A.
AU - Albers, Sonja Verena
N1 - Publisher Copyright:
© 2015 The Authors.
PY - 2015/5/5
Y1 - 2015/5/5
N2 - 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-Å and 1.65-Å resolution crystal structures of this monotopic membrane protein. Structures revealed an N-terminal α-helix and an eight-strand β-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.
AB - 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-Å and 1.65-Å resolution crystal structures of this monotopic membrane protein. Structures revealed an N-terminal α-helix and an eight-strand β-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.
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U2 - 10.1016/j.str.2015.03.001
DO - 10.1016/j.str.2015.03.001
M3 - Article
C2 - 25865246
AN - SCOPUS:84930190732
SN - 0969-2126
VL - 23
SP - 863
EP - 872
JO - Structure
JF - Structure
IS - 5
ER -