PDF(Pubmed)
Abstract：
Myosin 5c (Myo5c) is a motor protein that is produced in epithelial and glandular tissues, where it plays an important role in secretory processes. Myo5c is composed of two heavy chains, each containing a generic motor domain, an elongated neck domain consisting of a single α-helix with six IQ motifs, each of which binds to a calmodulin (CaM) or a myosin light chain from the EF-hand protein family, a coiled-coil dimer-forming region and a carboxyl-terminal globular tail domain. Although Myo5c is a low duty cycle motor, when two or more Myo5c-heavy meromyosin (HMM) molecules are linked together, they move processively along actin filaments. We describe the purification and functional characterization of human Myo5c-HMM co-produced either with CaM alone or with CaM and the essential and regulatory light chains Myl6 and Myl12b. We describe the extent to which cofilaments of actin and Tpm1.6, Tpm1.8 or Tpm3.1 alter the maximum actin-activated ATPase and motile activity of the recombinant Myo5c constructs. The small allosteric effector pentabromopseudilin (PBP), which is predicted to bind in a groove close to the actin and nucleotide binding site with a calculated ΔG of -18.44 kcal/mol, inhibits the motor function of Myo5c with a half-maximal concentration of 280 nM. Using immunohistochemical staining, we determined the distribution and exact localization of Myo5c in endothelial and endocrine cells from rat and human tissue. Particular high levels of Myo5c were observed in insulin-producing β-cells located within the pancreatic islets of Langerhans.
摘要：
肌球蛋白5c（Myo5c）是一种运动蛋白，在上皮组织和腺体组织中产生，它在分泌过程中起着重要作用。Myo5c由两条重链组成，每个都包含一个通用的运动域，由单个α-螺旋和六个IQ基序组成的细长颈部结构域，每个都与EF-hand蛋白家族的钙调蛋白（CaM）或肌球蛋白轻链结合，卷曲螺旋二聚体形成区和羧基末端球状尾结构域。虽然Myo5c是低占空比电机，当两个或多个Myo5c-重质肌球蛋白（HMM）分子连接在一起时，它们沿着肌动蛋白丝顺序移动。我们描述了与CaM单独或与CaM以及必需和调节轻链Myl6和Myl12b共同产生的人Myo5c-HMM的纯化和功能表征。我们描述了肌动蛋白和Tpm1.6，Tpm1.8或Tpm3.1的辅丝改变重组Myo5c构建体的最大肌动蛋白激活的ATPase和运动活性的程度。小变构效应物五羟甲基溴(PBP)，预测其结合在靠近肌动蛋白和核苷酸结合位点的凹槽中，计算的ΔG为-18.44kcal/mol，以280nM的半最大浓度抑制Myo5c的运动功能。使用免疫组织化学染色，我们确定了Myo5c在大鼠和人体组织的内皮和内分泌细胞中的分布和精确定位。在位于朗格汉斯胰岛内的产生胰岛素的β细胞中观察到特别高水平的Myo5c。
