Kengyel András, Palarz Philip M, Krohn Jacqueline, Marquardt Anja, Greve Johannes N, Heiringhoff Robin, Jörns Anne, Manstein Dietmar J
Institute for Biophysical Chemistry, Hannover Medical School, Hannover, Germany.
Department of Biophysics, University of Pécs Medical School, Pécs, Hungary.
Front Physiol. 2024 Mar 28;15:1394040. doi: 10.3389/fphys.2024.1394040. eCollection 2024.
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.
肌球蛋白5c（Myo5c）是一种在上皮组织和腺组织中产生的运动蛋白，它在分泌过程中发挥着重要作用。Myo5c由两条重链组成，每条重链都包含一个通用的运动结构域、一个由单个α-螺旋组成的细长颈部结构域，该颈部结构域带有六个IQ基序，每个IQ基序都与钙调蛋白（CaM）或来自EF-手蛋白家族的肌球蛋白轻链结合、一个卷曲螺旋二聚体形成区域以及一个羧基末端球状尾部结构域。尽管Myo5c是一种低占空比的运动蛋白，但当两个或更多的Myo5c-重酶解肌球蛋白（HMM）分子连接在一起时，它们会沿着肌动蛋白丝进行连续移动。我们描述了单独与CaM一起或与CaM以及必需轻链和调节轻链Myl6和Myl12b共同产生的人Myo5c-HMM的纯化及功能特性。我们描述了肌动蛋白与Tpm1.6、Tpm1.8或Tpm3.1的共丝对重组Myo5c构建体的最大肌动蛋白激活ATP酶和运动活性的影响程度。小的变构效应物五溴假丝菌素（PBP）预计以-18.44千卡/摩尔的计算自由能结合在靠近肌动蛋白和核苷酸结合位点的凹槽中，它以280 nM的半数最大浓度抑制Myo5c的运动功能。通过免疫组织化学染色，我们确定了Myo5c在大鼠和人类组织的内皮细胞和内分泌细胞中的分布及确切定位。在位于胰岛中的产生胰岛素的β细胞中观察到了特别高的Myo5c水平。
