COMPARATIVE BIOCHEMICAL AND MORPHOLOGICAL STUDIES ON A DYNEIN MOLECULE

动力蛋白是一种分子马达，负责许多不同类型的微管运动。在纤毛和鞭毛中，动力蛋白包含在内臂和外臂中，产生纤毛和鞭毛弯曲所需的力。外臂动力蛋白可能是所有动力蛋白异构体中研究最广泛的。对包括哺乳动物、被囊动物、棘皮动物、软体动物、环节动物、节肢动物、扁虫和海葵在内的各种动物的精子鞭毛和纤毛的横切面的检查表明，它们的外臂是钩状或拳头状的，与衣单胞菌、草笋虫和四膜虫的手枪状形成鲜明对比。由此可见，原生动物鞭毛和纤毛的外臂动力蛋白分子为三头结构，后生动物精子鞭毛的外臂动力蛋白分子为双头结构。海胆精子轴索外臂动力蛋白包含三个中间链（IC1、IC2和IC3； Mr分别为128,000、98,000和74,000）。在本研究中，我们克隆了所有的中间链。IC2和IC3是WD家族的成员；WD基序负责蛋白质与蛋白质的相互作用。IC1具有独特的一级结构，n端部分与硫氧还蛋白序列同源，中间部分由三个重复序列组成，与核苷二磷酸激酶序列同源，c端部分含有高比例的带负电荷的谷氨酸残基。因此，IC1是一种不同于IC2和IC3的新型动力蛋白中间链，可能是一种多功能蛋白。此外，还获得了海胆精子轴突中动力蛋白臂的双向动力行程的证据。

Dyneins are molecular motors responsible for many different types of microtubule-based motility. Within cilla and flagella, dyneins are contained in the inner and outer arms and generate the force required for ciliary and flagellar bending. The outer arm dynein is probably the most extensively studied of all dynein isoforms.Examination of the cross-sections of sperm flagella and cilia in various animals, including mammals, tunicates, echinoderms, molluses, annelids, arthropods, flatworms and sea anemones, indicates that their outer arms are hook-or fist-like, in contrast to the pistol-like shape in Chlamydomonas, Paramecium, and Tetrahymena. Thus, it may be concluded that the outer arm dynein molecules of flagella and cilia in Protozoa has a three-headed structure, whereas that of sperm flagella in Metazoa exhibits a two-headed structure.The outer arm dynein of sea urchin sperm axoneme contains three intermediate chains (IC1, IC2, and IC3 ; Mr 128,000,98,000, and 74,000, respectively). In the present study, we cloned all the intermediate chains. IC2 and IC3 are members of the WD family ; the WD motif is responsible for a protein-protein interaction. IC1 has a unique primary structure, the N-terminal part is homologous to the sequence of thioredoxin, the middle part consists of three repetitive sequences homologous to the sequence of nucleoside diphosphate kinase, and the C-terminal part contains a high proportion of negatively charged glutamic acid residues. Thus, IC1 is a novel dynein intermediate chain distinct from IC2 and IC3 and may be a multifunctional protein.In addition, a piece of evidence was obtained to indicate bidirectional power stroke of the dynein arms in sea urchin sperm axonemes.