Proteolysis of truncated hemolysin A yields a stable dimerization interface

Wild-type and variant forms of HpmA265 (truncated hemolysin A) from Proteus mirabilis reveal a right-handed, parallel β -helix capped and flanked by segments of antiparallel β -strands. The low-salt crystal structures form a dimeric structure via the implementation of on-edge main-chain hydrogen bonds donated by residues 243 – 263 of adjacent monomers. Surprisingly, in the high-salt structures of two variants, Y134A and Q125A-Y134A, a new dimeric interface is formed via main-chain hydrogen bonds donated by residues 203 – 215 of adjacent monomers, and a previously unobserved tetramer is formed. In addition, an eight-stranded antiparallel β -sheet is formed from the flap regions of crystallographically related monomers in the high-salt structures. This new interface is possible owing to additional proteolysis of these variants after Tyr240. The interface formed in the high-salt crystal forms of hemolysin A variants may mimic the on-edge β -strand positioning used in template-assisted hemolytic activity.

Source: Acta Crystallographica Section F - February 20, 2017 Category: Biochemistry Authors: Novak, W.R.P. Bhattacharyya, B. Grilley, D.P. Weaver, T.M. Tags: hemolysin A two-partner secretion alternate crystal forms proteolysis β -helix Proteus mirabilis research communications Source Type: research