Bonafé N, Sellers J R
National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892-1762, USA.
J Muscle Res Cell Motil. 1998 Feb;19(2):129-41. doi: 10.1023/a:1005356511634.
Recent studies have revealed unconventional myosin V to be an important actin-based molecular motor involved in vesicular movement. In this paper we report the molecular characterization of the Drosophila myosin V, identified by reverse genetics. The gene encodes a 1792-residue, 207 kDa heavy chain polypeptide which possesses a typical head or motor domain of 771 residues, a region of six IQ motifs (139 residues) which serve as potential calmodulin/light chain binding sites at the head/tail junction, and a tail domain of 882 residues containing sequences of putative alpha-helical coiled-coils required for dimerization of the molecule and sequences of non-helical structure at the C-terminal end. Based on Southern blot analyses and chromosomal localization, evidence is presented for a single Drosophila myosin V gene. RNA analyses revealed a doublet of transcripts of about 6 kb, expressed throughout the lifetime of a fly but particularly abundant in the early stages of embryonic development (maternally contributed), in the ectodermic tissue of the hindgut starting at stage 16, and in the adult head. These results suggest that myosin V may be involved in processes required in a variety of cell types in Drosophila. We have also mapped the Drosophila myosin V locus to chromosome 2 at the position 43C-D, and we are currently searching for known mutations in this region. Finally, phylogenetic analysis of the head domain reveals that Drosophila myosin V is more closely related to mammalian myosin Va and Vb than to other invertebrate class-V myosins; nevertheless, it is not significantly more related to myosin Va than to myosin Vb. While vertebrates would need two different myosin V isoforms to accomplish specific functions, we speculate that Drosophila myosin V might provide the equivalent functions by itself.
最近的研究表明，非常规肌球蛋白V是一种重要的基于肌动蛋白的分子马达，参与囊泡运动。在本文中，我们报告了通过反向遗传学鉴定的果蝇肌球蛋白V的分子特征。该基因编码一个1792个残基、207 kDa的重链多肽，其具有一个由771个残基组成的典型头部或马达结构域、一个由六个IQ模体（139个残基）组成的区域，该区域在头部/尾部连接处作为潜在的钙调蛋白/轻链结合位点，以及一个由882个残基组成的尾部结构域，其中包含分子二聚化所需的假定α-螺旋卷曲螺旋序列和C末端的非螺旋结构序列。基于Southern印迹分析和染色体定位，有证据表明果蝇中存在单个肌球蛋白V基因。RNA分析显示有一个约6 kb的转录本双峰，在果蝇的整个生命周期中都有表达，但在胚胎发育早期（母源贡献）、从第16阶段开始的后肠外胚层组织以及成年头部中特别丰富。这些结果表明肌球蛋白V可能参与果蝇多种细胞类型所需的过程。我们还将果蝇肌球蛋白V基因座定位到2号染色体上的43C-D位置，目前正在搜索该区域的已知突变。最后，头部结构域的系统发育分析表明，果蝇肌球蛋白V与哺乳动物肌球蛋白Va和Vb的关系比与其他无脊椎动物V类肌球蛋白更密切；然而，它与肌球蛋白Va的关系并不比与肌球蛋白Vb的关系更显著。虽然脊椎动物需要两种不同的肌球蛋白V同工型来完成特定功能，但我们推测果蝇肌球蛋白V可能自身就能提供等效功能。
