Molecular modeling of manganese regulation of calmodulin-sensitive adenylyl cyclase from mammalian sperm |
| |
Authors: | Toscano William A Toscano John S Toscano Diane G Gross Mary K |
| |
Institution: | Division of Environmental and Occupational Health, University of Minnesota School of Public Health, Minneapolis, MN 55455, USA. tosca001@umn.edu |
| |
Abstract: | The soluble calmodulin-sensitive isoform of adenylyl cyclase isolated from equine sperm is unique because it requires Mn(2+) rather than Mg(2+) for activity. To gain insight into the molecular action of metals on sperm adenylyl cyclase, the kinetics of Mn(2+) and ATP effect was examined. A biphasic response to increases in ATP concentration was observed when metal was held constant. When Mn(2+)] exceeded ATP], however, greatly enhanced enzyme activity was observed. The kinetic profiles were consistent with allosteric activation of adenylyl cyclase by Mn(2+). Linear transformation of the data yielded an apparent K(m) for Mn-ATP of 5.8 mM and calculated V(max) of 12 nM cyclic AMP formed/min/mg. Data analysis using calculated equilibrium concentrations of free and complexed reactants provided similar estimates of these kinetic parameters. |
| |
Keywords: | Cyclic nucleotides Signal transduction Metal ions Molecular modeling Kinetics Allostery Fertility Sperm motility |
本文献已被 ScienceDirect PubMed 等数据库收录! |