TY - JOUR
T1 - Unperturbing a non-helically perturbed bacterial flagellar filament
T2 - Salmonella typhimurium SJW23
AU - Nisani-Bizer, Keren
AU - Trachtenberg, Shlomo
PY - 2012/2/24
Y1 - 2012/2/24
N2 - Salmonella typhimurium SJW23 has a right-handed, non-helically perturbed filament of serotype gt with a unique surface pattern. Non-helical perturbations involve symmetry reduction along the five-start helical lines resulting in layer lines of fractional Bessel orders and a consequent seam. The flagellin gene, fliC23, which we sequenced, differs from the sequence of the canonic, plain SJW1655 flagellin, fliC1655. We modified discrete components of fliC23 in order to localize, in the expressed filament, the submolecular site responsible for the non-helical perturbation. These modifications include (i) deleting the outermost domain D323, (ii) replacing D323 with D31655, (iii) substituting a hydrophilic α-helix at the interface between the neighboring domains D1 and D2 with a hydrophobic one from fliC1655, and (iv) substituting a serine/glycine pair in the loop connecting the modified α-helix to its neighbor; these modifications were made in the presence and absence of D3 23. We used S. typhimurium SJW1655 both as a reference and as a source for 'spare parts'. The symmetry of the constructs was assessed from the power spectra through changes in the layer lines at a height of «1/105» and «1/35» Å- 1, unique to the non-helical perturbation. Deleting D323, either alone or in combination with various substitutions, or replacing it with D31655 transforms the non-helically perturbed filament into a plain one as judged by the disappearance of the typical layer lines from the power spectra. We conclude that the non-helical perturbation is a product of unique interactions in the D323 density shell. Whereas other minor structural changes may occur at the filaments interior, they are all helically symmetric.
AB - Salmonella typhimurium SJW23 has a right-handed, non-helically perturbed filament of serotype gt with a unique surface pattern. Non-helical perturbations involve symmetry reduction along the five-start helical lines resulting in layer lines of fractional Bessel orders and a consequent seam. The flagellin gene, fliC23, which we sequenced, differs from the sequence of the canonic, plain SJW1655 flagellin, fliC1655. We modified discrete components of fliC23 in order to localize, in the expressed filament, the submolecular site responsible for the non-helical perturbation. These modifications include (i) deleting the outermost domain D323, (ii) replacing D323 with D31655, (iii) substituting a hydrophilic α-helix at the interface between the neighboring domains D1 and D2 with a hydrophobic one from fliC1655, and (iv) substituting a serine/glycine pair in the loop connecting the modified α-helix to its neighbor; these modifications were made in the presence and absence of D3 23. We used S. typhimurium SJW1655 both as a reference and as a source for 'spare parts'. The symmetry of the constructs was assessed from the power spectra through changes in the layer lines at a height of «1/105» and «1/35» Å- 1, unique to the non-helical perturbation. Deleting D323, either alone or in combination with various substitutions, or replacing it with D31655 transforms the non-helically perturbed filament into a plain one as judged by the disappearance of the typical layer lines from the power spectra. We conclude that the non-helical perturbation is a product of unique interactions in the D323 density shell. Whereas other minor structural changes may occur at the filaments interior, they are all helically symmetric.
KW - bacterial flagella
KW - bacterial motility
KW - flagellin
KW - helical symmetry
KW - non-helical perturbations
UR - http://www.scopus.com/inward/record.url?scp=84856733940&partnerID=8YFLogxK
U2 - 10.1016/j.jmb.2012.01.003
DO - 10.1016/j.jmb.2012.01.003
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C2 - 22248588
AN - SCOPUS:84856733940
SN - 0022-2836
VL - 416
SP - 367
EP - 388
JO - Journal of Molecular Biology
JF - Journal of Molecular Biology
IS - 3
ER -