Figure 4.

G150A-PapA subunit alters the helical symmetry of the Pap pilus rod. The helical symmetry of pili purified from the bacterial cell surface containing wild-type (A), Y162F (B), and (C) G150A PapA was calculated as described (19). The symmetry of the Y162F pili is unchanged from wild type: 3.281 ± 0.006 with a helical pitch of 24.77 ± 0.87 Å (n = 27) vs. 3.279 ± 0.003 u/t with a helical pitch of 24.87 ± 0.41 Å (n = 21), respectively. The symmetry of the G150A pili is more variable and has a tighter twist, 3.287 ± 0.009 u/t and a helical pitch of 24.67 ± 1.18 Å (n = 32); i.e., this mutant has a larger standard deviation and more u/t of the helix than wild-type pili.