title: The properties and contribution of the Corynebacterium glutamicum MscS variant to fine-tuning of osmotic adaptation.
abstract: Based on sequence similarity, the mscCG gene product of Corynebacterium glutamicum belongs to the family of MscS-type mechanosensitive channels. In order to investigate the physiological significance of MscCG in response to osmotic shifts in detail, we studied its properties using both patch-clamp techniques and betaine efflux kinetics. After heterologous expression in an Escherichiacoli strain devoid of mechanosensitive channels, in patch-clamp analysis of giant E. coli spheroplasts MscCG showed the typical pressure dependent gating behavior of a stretch-activated channel with a current/voltage dependence indicating a strongly rectifying behavior. Apart from that, MscCG is characterized by significant functional differences with respect to conductance, ion selectivity and desensitation behavior as compared to MscS from E. coli. Deletion and complementation studies in C. glutamicum showed a significant contribution of MscCG to betaine efflux in response to hypoosmotic conditions. A detailed analysis of concomitant betaine uptake (by the betaine transporter BetP) and efflux (by MscCG) under hyperosmotic conditions indicates that MscCG may act in osmoregulation in C. glutamicum by fine-tuning the steady state concentration of compatible solutes in the cytoplasm which are accumulated in response to hyperosmotic stress.
authors.affiliation: Institute of Biochemistry, University of Cologne, 50674 Cologne, Germany.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Börngen
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Battle
authors.forename: Nina
authors.initials: N
authors.lastname: Möker
authors.forename: Susanne
authors.initials: S
authors.lastname: Morbach
authors.forename: Kay
authors.initials: K
authors.lastname: Marin
authors.forename: Boris
authors.initials: B
authors.lastname: Martinac
authors.forename: Reinhard
authors.initials: R
authors.lastname: Krämer
mesh_terms: D000222:Adaptation, Physiological; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism / Q000502:physiology*; D002352:Carrier Proteins / Q000378:metabolism; D048230:Corynebacterium glutamicum / Q000502:physiology*; D007473:Ion Channels / Q000502:physiology*; D008969:Molecular Sequence Data; D027981:Symporters; D014882:Water-Electrolyte Balance
chemical_list: D001426:Bacterial Proteins; C101652:BetP protein, Corynebacterium glutamicum; D002352:Carrier Proteins; D007473:Ion Channels; D027981:Symporters