User:Fadel A. Samatey/FlhBc I

Salmonella

FlhB from Salmonella typhimurium consists of 383 amino acids. The cytoplasmic domain 219-383 (length 165, 43% of full length) was crystallized. The resulting model 3b0z includes coordinates for residues 229-353 (length 125, 76% of the crystallized length). The asymmetric unit contains a single molecule ().

As explained in the publication, the position of the long alpha helix appears to be stabilized by crystal contacts (not shown).

The chain is . This is believed to be autocatalytic cleavage involved in the transition of the export apparatus from hook to filament mode. Mutations that prevent this cleavage render the bacteria non-motile.

Aquifex

FlhB from the thermophile^[1] Aquifex aeolicus is shorter, 350 residues (vs. 383 for S. typhimurium), with 32% sequence identity. Residues 213-350 (length 138) were crystallized, and the resulting model 3b1s has in the asymmetric unit. The molecule displayed in the comparison in the next section, with chains designated C and D, was chosen because it has the lowest average temperature factor (66.2, vs. 84.7 and 72.6 for A,B and E,F respectively). It has coordinates for 232-337 (length 106, 77% of the crystallized segment), cleaved at NPTH between Asn263 and Pro264.

Comparison

The FlhBc Salmonella 3D structure is very similar to that of Aquifex. 102 alpha carbons align with an RMSD of 1.0 Å. Their FlhB's have 32% sequence identity. , then click the button below to do a structural alignment.

Loop 281-285

Both FlhBc structures have a protruding loop, which in Salmonella is 281-285. Despite the fact that this loop is not conserved (see below), its deletion abolished motility. Mutation of the loop