Hernández E O, Trejo R, Espinosa A M, González A, Mújica A
Departamento de Biología Celular, Instituto Politécnico Nacional, México, D.F. México.
Tissue Cell. 1994 Dec;26(6):849-65. doi: 10.1016/0040-8166(94)90036-1.
Calmodulin has been suggested as the Ca(2+)-mediator in diverse cellular functions via its interaction with a number of proteins in a calcium-dependent manner. Its participation in the acrosome reaction has been suggested based on its localization in the acrosome region, on the effects produced by calmodulin antagonists, and by the changes in calmodulin compartmentation observed to occur throughout guinea pig acrosome reaction. To define the role of calmodulin in the membrane fusion events that occur during the acrosome reaction, the identification of calmodulin-binding proteins, by the overlay technique with biotinylated or unmodified calmodulin, was made in the following sperm fractions: in the membrane vesicles released during the acrosome reaction, in the remaining perinuclear material of acrosome reacted sperm heads and in a total membrane fraction from intact spermatozoa. The membrane vesicles released after the acrosome reaction showed four major calmodulin-binding proteins, M(r)s 66, 95, 97 and 110 kDa. The perinuclear material showed a 31-34, 43 and 97 kDa calmodulin-binding polypeptides. The membrane fraction from intact sperm showed eleven calmodulin-binding proteins, M(r)s between 14-110 kDa. Most of the binding proteins detected by this method corresponded to the class of calcium-independent calmodulin-binding proteins but proteins which only interacted with calmodulin in a calcium-inhibited mode were also observed. No calcium-dependent calmodulin-binding proteins were detected in any of the fractions studied. A possible role of these binding proteins in calmodulin compartmentation is discussed. The potential role of these binding proteins in membrane fusion and in membrane receptor localization in the postacrosomal region remain to be defined.
钙调蛋白已被认为是通过其与多种蛋白质以钙依赖方式相互作用，在多种细胞功能中起钙离子介导作用。基于其在顶体区域的定位、钙调蛋白拮抗剂产生的效应以及在豚鼠顶体反应过程中观察到的钙调蛋白区室化变化，提示了其参与顶体反应。为了确定钙调蛋白在顶体反应过程中发生的膜融合事件中的作用，通过用生物素化或未修饰的钙调蛋白进行覆盖技术，在以下精子组分中鉴定钙调蛋白结合蛋白：在顶体反应期间释放的膜囊泡中、在顶体反应后的精子头部剩余的核周物质中以及在完整精子的总膜组分中。顶体反应后释放的膜囊泡显示出四种主要的钙调蛋白结合蛋白，分子量分别为66、95、97和110 kDa。核周物质显示出分子量为31 - 34、43和97 kDa的钙调蛋白结合多肽。完整精子的膜组分显示出十一种钙调蛋白结合蛋白，分子量在14 - 110 kDa之间。通过该方法检测到的大多数结合蛋白属于非钙依赖性钙调蛋白结合蛋白类别，但也观察到仅以钙抑制模式与钙调蛋白相互作用的蛋白质。在所研究的任何组分中均未检测到钙依赖性钙调蛋白结合蛋白。讨论了这些结合蛋白在钙调蛋白区室化中的可能作用。这些结合蛋白在膜融合和顶体后区域膜受体定位中的潜在作用仍有待确定。
