Acinetobacter baylyi CarO is a channel for basic amino acids and positively charged substrates

RELLING V.; MUSSI M.A.; LIMANSKY A.; VIALE A.

Tucumán. Argentina

Congreso; XLV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2009

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB)

CarO, an outer membrane protein (OMP) member of a family only present in the family Moraxellaceae, is related to imipenem (IPM) resistance among clinical Acinetobacter baumannii strains. However, the physiological function of members of the family is still unknown. Acinetobacter baylyi represents a valuable genetic tool and useful model to study the role of genus-specific proteins. To obtain clues on a general role of CarO in the genus we previously constructed carO deletion mutants (ÄcarO) and evaluated their growth capabilities on different carbon sources. The mutants exhibited reduced rates of growth on L-arginine and increased resistance to IPM as judged by comparisons of minimal inhibitory concentration (MIC) values towards this antibiotic. MIC values determined for A. baylyi in medium supplemented with different substrates indicated that positively charged amino acids and amines acted as the most effective competitors of IPM uptake. We further characterized A. bayly CarO roles in IPM uptake by kinetic studies using wt and ÄcarO bacteria transformed with a plasmid directing production of a periplasmatic (VIM-2) imipenemase. These studies indicated that A. baylyi CarO provides a saturable, specific OM channel for IPM, and competition for IPM permeation by Larginine supported the above notion that CarO may serve physiological channel roles for positively charged substrates.Acinetobacter baylyi represents a valuable genetic tool and useful model to study the role of genus-specific proteins. To obtain clues on a general role of CarO in the genus we previously constructed carO deletion mutants (ÄcarO) and evaluated their growth capabilities on different carbon sources. The mutants exhibited reduced rates of growth on L-arginine and increased resistance to IPM as judged by comparisons of minimal inhibitory concentration (MIC) values towards this antibiotic. MIC values determined for A. baylyi in medium supplemented with different substrates indicated that positively charged amino acids and amines acted as the most effective competitors of IPM uptake. We further characterized A. bayly CarO roles in IPM uptake by kinetic studies using wt and ÄcarO bacteria transformed with a plasmid directing production of a periplasmatic (VIM-2) imipenemase. These studies indicated that A. baylyi CarO provides a saturable, specific OM channel for IPM, and competition for IPM permeation by Larginine supported the above notion that CarO may serve physiological channel roles for positively charged substrates.