Genetic and biochemical characterization of a high-affinity betaine uptake system (BusA) in Lactococcus lactis reveals a new functional organization within bacterial ABC transporters.

ABSTRACT: The cytoplasmic accumulation of exogenous betaine stimulates the growth of Lactococcus lactis cultivated under hyperosmotic conditions. We report that L. lactis possesses a single betaine transport system that belongs to the ATP-binding cassette (ABC) superfamily of transporters. Through transposon mutagenesis, a mutant deficient in betaine transport was isolated. We identified two genes, busAA and busAB, grouped in an operon, busA (betaine uptake system). The transcription of busA is strongly regulated by the external osmolality of the medium. The busAA gene codes for the ATP-binding protein. busAB encodes a 573-residue polypeptide which presents two striking features: (i) a fusion between the regions encoding the transmembrane domain (TMD) and the substrate-binding domain (SBD) and (ii)

SUBMITTER: Obis D 

PROVIDER: S-EPMC103755 | biostudies-literature | 1999 Oct

REPOSITORIES: biostudies-literature