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Journal of Bacteriology, April 1999, p. 2267-2272, Vol. 181, No. 7
Unité de Programmation
Moléculaire et Toxicologie Génétique, CNRS URA
1444, Institut Pasteur, F75724 Paris Cedex 15, France
Received 13 October 1998/Accepted 28 January 1999
MalF is one of the two integral inner membrane proteins of the
maltose-maltodextrin transport system. To identify functional regions
in this protein, we characterized a collection of malF mutants obtained by random mutagenesis. We analyzed their growth on
maltose and maltodextrins, the steady-state levels and subcellular localization of the mutant proteins, and the subcellular localization of MalK. Only 2 of the 21 MalF mutant proteins allowed growth on
maltose and maltodextrins. Most mutations resulting in immunodetectable proteins mapped to hydrophilic domains, indicating that insertions affecting transmembrane segments gave rise to unstable or lethal proteins. All MalF mutant proteins, even those C-terminally truncated or with large N-terminal deletions, were inserted into the
cytoplasmic membrane. Having identified mutations leading to
reduced steady-state level, to partial mislocation, and/or to
misfolding, we were able to assign to some regions of MalF a role in
the assembly of the MalFGK2 complex and/or in the transport mechanism.
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Structure-Function Study of MalF Protein by Random
Mutagenesis
*
Corresponding author. Mailing address: Unité de
Programmation Moléculaire et Toxicologie Génétique,
CNRS URA 1444, Institut Pasteur, 25 rue du Dr. Roux, F75724 Paris Cedex
15, France. Phone: 33 (0)1 45 68 88 31. Fax: 33 0(1) 45 68 88 34. E-mail: elidassa{at}pasteur.fr.
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