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J. Bacteriol. doi:10.1128/JB.01032-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

L-Rhamnose Transport is Sugar-Kinase (RhaK) Dependent in Rhizobium leguminosarum bv. trifolii

Dept. of Microbiology, University of Manitoba, Winnipeg, MB, Canada

^* To whom correspondence should be addressed. Email: oresniki{at}cc.umanitoba.ca.

	Abstract

Strains of R. leguminosarum unable to catabolize L-rhamnose, a methyl-pentose sugar, are compromised in their ability to compete for nodule occupancy versus wild-type strains. Previous characterization of the 11-kb region necessary for the utilization of rhamnose identified a locus encoding catabolic genes and the components of an ABC transporter. Genetic evidence suggested that the putative kinase, RhaK, carried out the first step in the catabolism of rhamnose. Characterization of this kinase has led to the observation that strains carrying rhamnose kinase mutations were unable to transport rhamnose into the cell. The absence of a functional rhamnose kinase did not stop the transcription and translation of the ABC transporter components. By developing an in vitro assay for RhaK activity we have been able to show that: (1) RhaK activity is consistent with RhaK phosphorylating rhamnose; (2) Biochemical activity of RhaK is necessary for rhamnose transport.

This article has been cited by other articles:

• Richardson, J. S., Carpena, X., Switala, J., Perez-Luque, R., Donald, L. J., Loewen, P. C., Oresnik, I. J. (2008). RhaU of Rhizobium leguminosarum Is a Rhamnose Mutarotase. J. Bacteriol. 190: 2903-2910 [Abstract] [Full Text]