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D RayChaudhuri

Publications and source records attributed to D RayChaudhuri.

6 recordsLinked to original sources
PubMed1999

ZipA is a MAP-Tau homolog and is essential for structural integrity of the cytokinetic FtsZ ring during bacterial cell division.

The first visible event in prokaryotic cell division is the assembly of the soluble, tubulin-like FtsZ GTPase into a membrane-associated cytokinetic ring that defines the division plane in bacterial and archaeal cells. In the temperature-sensitive ftsZ84 mutant of Escherichia coli, this ring assembly is impaired at the restrictive temperature causing lethal cell filamentation. Here I present genetic and morphological evidence that a 2-fold higher dosage of the division gene zipA suppresses thermosensitivity of the ftsZ84 mutant by stabilizing the labile FtsZ84 ring structure in vivo. I demonstrate that purified ZipA promotes and stabilizes protofilament assembly of both FtsZ and FtsZ84 in vitro and cosediments with the protofilaments. Furthermore, ZipA organizes FtsZ protofilaments into arrays of long bundles or sheets that probably represent the physiological organization of the FtsZ ring in bacterial cells. The N-terminal cytoplasmic domain of membrane-anchored ZipA contains sequence elements that resemble the microtubule-binding signature motifs in eukaryotic Tau, MAP2 and MAP4 proteins. It is postulated that the MAP-Tau-homologous motifs in ZipA mediate its binding to FtsZ, and that FtsZ-ZipA interaction represents an ancient prototype of the protein-protein interaction that enables MAPs to suppress microtubule catastrophe and/or to promote rescue.

Amino Acid Sequence↗
PubMed1994

A point mutation converts Escherichia coli FtsZ septation GTPase to an ATPase.

The cell division protein FtsZ, essential to initiate septum formation in Escherichia coli, is a GTPase. The thermosensitive ftsZ84 mutation, which impairs the ability of FtsZ to bind and hydrolyze GTP in vitro, maps to a short glycine-rich FtsZ segment. This region is conserved in eubacterial FtsZ homologs and is strikingly similar to the proposed GTP binding motif in the eukaryotic cytoskeletal protein tubulin. Here we show that in contrast to FtsZ, FtsZ84 protein has a Mg(2+)-dependent ATPase activity in vitro. This activity, unlike the wild-type GTPase, is specifically inhibited by sodium azide, a known antagonist of F-type ATPases and the bacterial SecA protein translocation ATPase (Oliver, D., Cabelli, R. J., Dolan, K. M., and Jarosik, G. P. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 8227-8231). Conversely, aluminum fluoride abolishes FtsZ GTPase activity but only partially affects FtsZ84 ATPase. Affinity-purified anti-FtsZ antibody blocks FtsZ84 ATPase activity, indicating that this enzymatic function is intrinsic to the mutant protein. This is, to our knowledge, the first example of a missense mutation that converts a GTPase to an ATPase.

Adenosine Triphosphatases↗
PubMed1992

Escherichia coli cell-division gene ftsZ encodes a novel GTP-binding protein.

Escherichia coli divides by forming a septum across the middle of the cell. The biochemical mechanism underlying this process is unknown. Genetic evidence suggests that of all the fts (filamentation temperature sensitive) genes involved in E. coli cell division, ftsZ plays a central role at the earliest known step of septation. Here we show that FtsZ protein binds GTP in vitro using unusual sequence elements. In contrast, such binding to the product of the conditional-lethal ftsZ84 allele is impaired. Purified FtsZ displays a Mg(2+)-dependent GTPase activity which is markedly reduced in the FtsZ84 protein. FtsZ copurifies with near stoichiometric amounts of noncovalently-bound GDP, implying the presence of a GTPase cycle in vivo, similar to that known for signal-transducing GTP-binding proteins. We also show that a small fraction of FtsZ exists as a distinct membrane-associated species that binds GTP. The membrane association of FtsZ and the known ability of GTPases to act as molecular switches implicate FtsZ in a GTP-activated signal transduction pathway that may regulate the start of septation in E. coli.

Amino Acid Sequence↗