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|Title:||Cooperative substrate binding by a diguanylate cyclase|
|Author:||Oliveira, Maycon C.|
Teixeira, Raphael D.
Andrade, Maxuel O.
Pinheiro, Glaucia M. S.
Ramos, Carlos H. I.
Farah, Chuck S.
|Abstract:||XAC0610, from Xanthomonas citri subsp. citri, is a large multi-domain protein containing one GAF (cGMP-specific phosphodiesterases, adenylyl cyclases and FhlA) domain, four PAS (Per-Arnt-Sim) domains and one GGDEF domain. This protein has a demonstrable in vivo and in vitro diguanylate cyclase (DGC) activity that leads to the production of cyclic di-GMP (c-di-GMP), a ubiquitous bacterial signaling molecule. Analysis of a Xac Delta 0610 knockout strain revealed that XAC0610 plays a role in the regulation of Xac motility and resistance to H2O2. Site-directed mutagenesis of a conserved DGC lysine residue (Lys759 in XAC0610) resulted in a severe reduction in XAC0610 DGC activity. Furthermore, experimental and in silico analyses suggest that XAC0610 is not subject to allosteric product inhibition, a common regulatory mechanism for DGC activity control. Instead, steady-state kinetics of XAC0610 DGC activity revealed a positive cooperative effect of the GTP substrate with a dissociation constant for the binding of the first GTP molecule (K-1) approximately 5x greater than the dissociation constant for the binding of the second GTP molecule (K-2). We present a general kinetics scheme that should be used when analyzing DGC kinetics data and propose that cooperative GTP binding could be a common, though up to now overlooked, feature of these enzymes that may in some cases offer a physiologically relevant mechanism for regulation of DGC activity in vivo|
|Subject:||Cinetica de enzimas|
|Appears in Collections:||IQ - Artigos e Outros Documentos|
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