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  Topic: more flag refs, the old thread seems stuck< Next Oldest | Next Newest >  
niiicholas



Posts: 319
Joined: May 2002

(Permalink) Posted: June 13 2003,01:11   

One more:

MG writes:

Quote

The truly interesting stuff comes from the FliI and F ATPase subunit comparison. The essence of their similarity revolves around the ATP-binding domain. At first glance, this doesnít seem too useful in distinguishing between common design and common descent, as one might expect ATP-binding motifs to be reused in different contexts from either perspective. But what seemed to indicate a hodgepodge use of this motif was that it appeared to be used as a monomer in the flagella. There didnít seem to be any type of design logic behind its reuse.
Your logic is none too clear here, but you seem to be under the misapprehension that the similarity between F1-beta and FliI was thought to be just a matter of the ATP-binding motif.  This is not what I've gathered:

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The proteins needed for flagella rotation include one that has antibody reactivity like and extensive sequence homology with the ATP synthase beta-subunit (243)

(Boyer 1997, Ann Rev Biochem, "The ATP synthase -- a splendid molecular machine, p. 743)
Ref #243 is:

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J Bacteriol. 1993 May;175(10):3131-8.

Genetic and biochemical analysis of Salmonella typhimurium FliI, a flagellar protein related to the catalytic subunit of the F0F1 ATPase and to virulence proteins of mammalian and plant pathogens.

Dreyfus G, Williams AW, Kawagishi I, Macnab RM.

Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511-8148.

FliI is a Salmonella typhimurium protein that is needed for flagellar assembly and may be involved in a specialized protein export pathway that proceeds without signal peptide cleavage. FliI shows extensive sequence similarity to the catalytic beta subunit of the F0F1 ATPase (A. P. Volger, M. Homma, V. M. Irikura, and R. M. Macnab, J. Bacteriol. 173:3564-3572, 1991). It is even more similar to the Spa47 protein of Shigella flexneri (M. M. Venkatesan, J. M. Buysse, and E. V. Oaks, J. Bacteriol. 174:1990-2001, 1992) and the HrpB6 protein of Xanthomonas campestris (S. Fenselau, I. Balbo, and U. Bonas, Mol. Plant-Microbe Interact. 5:390-396, 1992), which are believed to play a role in the export of virulence proteins. Site-directed mutagenesis of residues in FliI that correspond to catalytically important residues in the F1 beta subunit resulted in loss of flagellation, supporting the hypothesis that FliI is an ATPase. FliI was overproduced and purified almost to homogeneity. It demonstrated ATP binding but not hydrolysis. An antibody raised against FliI permitted detection of the protein in wild-type cells and an estimate of about 1,500 subunits per cell. An antibody directed against the F1 beta subunit of Escherichia coli cross-reacted with FliI, confirming that the proteins are structurally related. The relationship between three proteins involved in flagellar assembly (FliI, FlhA, and FliP) and homologs in a variety of virulence systems is discussed.
Finally, in support of the contention that the similarity is in excess of what can be accounted for simply by both proteins being ATP-binders, looking at Vogler et al.:

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Variants of motifs A and B are present in many ATP-utilizing enzymes.  However, the degree of agreement between these motifs in FliI and the F0F1 and related ATPases is generally stronger than that between FliI and the ATP-utilizing proteins generally...We conclude that FliI is specifically related to subunits of the F0F1, vacuolar, and archaeabacterial ATPases and not just generally related to nucleotide-binding or nucleotide-utilizing proteins as a whole.

(p. 3569, Vogler et al 1991, Jour. Bacteriology)

  
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