Title: FlaF Is a β-Sandwich Protein that Anchors the Archaellum in the Archaeal Cell Envelope by Binding the S-Layer Protein

Abstract

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.

Authors:

Banerjee, Ankan; Tsai, Chi-Lin; Chaudhury, Paushali; Tripp, Patrick; Arvai, Andrew S.; Ishida, Justin P.; Tainer, John A.; Albers, Sonja-Verena

Publication Date:

Fri May 01 00:00:00 EDT 2015

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1392695

Alternate Identifier(s):

OSTI ID: 1208647

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Published Article

Journal Name:

Structure

Additional Journal Information:

Journal Name: Structure Journal Volume: 23 Journal Issue: 5; Journal ID: ISSN 0969-2126

Publisher:

Elsevier

Country of Publication:

United Kingdom

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES