Kurvari V, Zhang Y, Luo Y, Snell W J
Department of Cell Biology and Neuroscience, University of Texas Southwestern Medical Center, Dallas 75235, USA.
Proc Natl Acad Sci U S A. 1996 Jan 9;93(1):39-43. doi: 10.1073/pnas.93.1.39.
Fertilization in Chlamydomonas is initiated by adhesive interactions between gametes of opposite mating types through flagellar glycoproteins called agglutinins. Interactions between these cell adhesion molecules signal for the activation of adenylyl cyclase through an interplay of protein kinases and ultimately result in formation of a diploid zygote. One of the early events during adhesion-induced signal transduction is the rapid inactivation of a flagellar protein kinase that phosphorylates a 48-kDa protein in the flagella. We report the biochemical and molecular characterization of the 48-kDa protein. Experiments using a bacterially expressed fusion protein show that the 48-kDa protein is capable of autophosphorylation on serine and tyrosine and phosphorylation of bovine beta-casein on serine, confirming that the 48-kDa protein itself has protein kinase activity. This protein kinase exhibits limited homology to members of the eukaryotic protein kinase superfamily and may be an important element in a signaling pathway in fertilization.
衣藻的受精过程是由相反交配型配子之间通过称为凝集素的鞭毛糖蛋白进行的粘附相互作用引发的。这些细胞粘附分子之间的相互作用通过蛋白激酶的相互作用发出信号，激活腺苷酸环化酶，最终导致二倍体合子的形成。粘附诱导信号转导过程中的早期事件之一是一种鞭毛蛋白激酶的快速失活，该激酶使鞭毛中的一种48 kDa蛋白磷酸化。我们报告了这种48 kDa蛋白的生化和分子特征。使用细菌表达的融合蛋白进行的实验表明，48 kDa蛋白能够在丝氨酸和酪氨酸上进行自磷酸化，并在丝氨酸上使牛β-酪蛋白磷酸化，证实该48 kDa蛋白本身具有蛋白激酶活性。这种蛋白激酶与真核蛋白激酶超家族成员的同源性有限，可能是受精信号通路中的一个重要元件。
