Multiple regulatory sites in the C-terminal autoinhibitory domain of the plasma membrane H+-ATPase

✍ Scribed by Anne Olsson; Fredrik Johansson; Marianne Sommarin; Christer Larsson

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 260 KB
• Volume: 8
• Category: Article
• ISSN: 0960-7412
• DOI: 10.1046/j.1365-313x.1995.8060959.x

✦ Synopsis

Summary

The H^+^‐ATPase activities of root and leaf plasma membranes from tobacco (Nicotiana tabacum) have been characterized with respect to V~max~, K~m~ for ATP, pH dependence and activation involving the C‐terminal autoinhibitory domain. With root plasma membranes, addition of lysophosphatidylcholine (lyso‐PC) resulted in the expected increase in V~max~, a decrease in K~m~(ATP), and a shift in pH optimum to a more alkaline pH, typical for activation via the C‐terminal inhibitory domain. With leaf plasma membranes, however, K~m~(ATP) was relatively low and the pH optimum was around pH 7.0 before the addition of lyso‐PC and did not change upon addition of the activator, although V~max~ increased twofold. Similar results were obtained with the in vivo activator fusicoccin. The results obtained with the leaf plasma membranes show that V~max~ may be regulated independently of K~m~(ATP) and pH optimum, and suggest the presence of at least two regulatory sites within the C‐terminal autoinhibitory domain of the H^+^‐ATPase.