Effect of Hook Subunit Concentration on Assembly and Control of Length of the Flagellar Hook of Salmonella

Abstract

The flagellar hook of Salmonella is a filamentous polymer made up of subunits of the protein FlgE. Hook assembly is terminated when the length reaches about 55 nm. After our recent study of the effect of cellular levels of the hook length control protein FliK, we have now analyzed the effect of cellular levels of FlgE itself. When FlgE was overproduced in a wild-type strain, afliC (flagellin) mutant, or a fliD(hook-associated protein 2 [HAP2], filament capping protein) mutant, the hooks remained at the wild-type length. In a fliK (hook length control protein) mutant, which produces long hooks (polyhooks), the overproduction of FlgE resulted in extraordinarily long hooks (superpolyhooks). In a flgK (HAP1, first hook-filament junction protein) mutant or a flgL (HAP3, second hook-filament junction protein) mutant, the overproduction of FlgE also resulted in longer than normal hooks. Thus, at elevated hook protein levels not only FliK but also FlgK and FlgL are necessary for the proper termination of hook elongation. When FlgE was severely underproduced, basal bodies without hooks were often observed. However, those hooks that were seen were of wild-type length, demonstrating that FlgE underproduction decreases the probability of the initiation of hook assembly but not the extent of hook elongation.

Molecular dissection of Salmonella FliH, a regulator of the ATPase FliI and the type III flagellar protein export pathway

“…When the deletion plasmids were used to transform the wild-type strain SJW1103 to test for dominance effects (relying on the high production levels of pTrc99A-based plasmids even in the absence of IPTG; Muramoto et al, 1999), the results were generally consistent with the complementation data ( Fig. 2, right).…”

“…[Combining deletions, not surprisingly, often increased the mutant phenotype (see above).] One possible explanation might be that the production levels from pTrc99A-based vectors, even when not induced with IPTG, are quite high (Muramoto et al, 1999) and might be sufficient to compensate for suboptimal function. However, we have carried out complementation using pET-based vectors (which have quite low expression in the absence of T7 polymerase) with essentially the same results (data not shown), and so this explanation seems unlikely.…”

An infrequent molecular ruler controls flagellar hook length inSalmonella enterica

“…More frequent measurement would increase the probability of a productive interaction of FliK with the secretion apparatus that would flip the specificity switch at a shorter hook length. Shorter hooks have indeed been observed under conditions where FliK measures hook length more frequently, for example over-expression of FliK (Muramoto et al, 1998;Minamino et al, 1999), underexpression of FlgE (Muramoto et al, 1999) or in a hook- Figure 7 Hook-length distribution of merodiploid strains co-expressing short and long FliK variants. Left panels: pellet and supernatant fractions were analysed by immunoblotting using polyclonal anti-FliK antibodies.…”

A tetratricopeptide repeat domain protein has profound effects on assembly of periplasmic flagella, morphology and motility of the lyme disease spirochete Borrelia burgdorferi

“…It is important to note that this type of non-homogenous phenotype seen in ΔfliL is common to the bacterial flagellar mutants. For example, in the ΔflgK, ΔflgL, ΔfliK or ΔmotB mutant, not all hooks or filaments are similar in size or number (Muramoto et al, 1999;Miller et al, 2014;Sultan et al, 2015). Since BB0236 and FlbB interact and FlbB forms the base of the collar, we propose that BB0236 assembles on FlbB (Fig.…”