Characterization of a K+ -ATPase from Lactobacillus helveticus ATCC 15009

• Published in: Archives of microbiology 1997, Vol.168 (3), p.205-209
• Main Authors: Solari, C, Panfoli, I, Morelli, A, Cassandrini, D, Cocconcelli, P, Morelli, L
• Format: Article
• Language: English
• Subjects: Bacteriology; Biological and medical sciences; dairy products; food microbiology; food processing; Fundamental and applied biological sciences. Psychology; Metabolism. Enzymes; Microbiology
• ISSN: 0302-8933; 1432-072X
• DOI: 10.1007/s002030050489

Lactobacillus helveticus ATCC 15009 (wild-type) membrane preparations hydrolyzed Mg2+-ATP as a function of K+ concentration (2-200 mM). Mg2+-ATP hydrolysis by L. helveticus membranes was strongly inhibited in the absence of exogenous K+, while it amounted to 6 nmol ATP hydrolyzed min-1 (mg membrane protein)-1 at 50 mM KCl (saturating conditions) and pH 7.2. The K+-dependent ATPase of L. helveticus displayed a relatively high affinity for potassium ions (Km = 800 micromolar) and was not affected by pretreatment of membranes with N,N'-dicyclohexylcarbodiimide. Membrane preparations were subjected to hypotonic shock to obtain a maximum yield of open profiles. The formation of a maximum level of enzyme-phosphate complex with a molecular mass of approximately 82 kDa was induced upon treatment of L. helveticus membrane preparations with low concentrations of [gamma-32P]ATP in the presence of K+ and La3+ ions and was visualized by acidic SDS-PAGE. It was concluded that L. helveticus membranes contain an inwardly directed K+ pump whose presence is discussed in terms of its putative role in cytoplasmic pH regulation.