RT Journal Article SR Electronic(1) A1 Moriya, Nao A1 Minamino, Tohru A1 Imada, Katsumi A1 Namba, KeiichiYR 2011 T1 Genetic analysis of the bacterial hook-capping protein FlgD responsible for hook assembly JF Microbiology, VO 157 IS 5 SP 1354 OP 1362 DO https://doi.org/10.1099/mic.0.047100-0 PB Microbiology Society, SN 1465-2080, AB FlgD of Salmonella enterica is a 232 aa protein that acts as the hook cap to promote assembly of FlgE into the hook structure. The N-terminal 86 residues (FlgDN) complement flgD mutants, albeit to a small degree. However, little is known about the role of the C-terminal region of FlgD (FlgDC). Here we isolated pseudorevertants from Salmonella flgE mutants. About half of the extragenic mutations lay within FlgDC and only one in FlgDN. These suppressor mutations prevented mutant FlgE subunits from leaking out to some degree. Two weakly motile flgD mutants encoding C-terminally truncated variants, FlgD(1-195) and FlgD(1-138f-s+4aa), secreted larger amounts of FlgE into the culture medium than wild-type cells. Their hooks were shorter, and their length distributions were broader, with significant tailing towards smaller values. These results suggest that FlgDC contributes to efficient hook polymerization. Therefore, we propose that FlgDN attaches to the distal end of the hook to promote hook polymerization and that FlgDC blocks the exit of newly exported FlgE monomers into the culture medium, allowing FlgE to have more time to assemble into the hook., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.047100-0