A novel class of unconventional myosins from Toxoplasma gondii
A novel class of unconventional myosins from Toxoplasma gondii
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DOI：
10.1006/jmbi.1997.1167
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发表时间：
1997-08-08
影响因子：
5.6
通讯作者：
Schwartzman, JD
中科院分区：
文献类型：
--
作者：
Heintzelman, MB;Schwartzman, JD
在这里，我们描述了完整的推导氨基酸序列的三个非常规肌球蛋白中确定的原生动物寄生虫弓形虫。系统发育分析表明，这三个肌球蛋白代表了一个新的，高度发散类除了肌球蛋白超家族。弓形虫肌球蛋白-A（Toxoplasma gondii myosin-A，TgM-A）是一种非常小的肌球蛋白，分子量约为93 kDa，与典型的肌球蛋白重链结构明显不同，具有头部和尾部结构域，但没有明显的颈部结构域。在其他肌球蛋白中，颈部由一个或多个IQ基序定义，其充当潜在的轻链结合结构域。在TgM-A中没有明显的IQ基序。TgM-A的尾部结构域仅包含57个氨基酸残基，其特征在于其高度碱性电荷（pI = 10.8）。另外两种弓形虫肌球蛋白TgM-B和TgM-C似乎是差异RNA剪接的产物，其中TgM-B产生约114 kDa的蛋白质，TgM-C产生约125 kDa的蛋白质。这两种肌球蛋白在它们的头部结构域和颈部结构域中是相同的，颈部结构域包含单个IQ基序。TgM-B和C共享其尾部结构域的近端245个残基，然后在其尾部结构远端发散。像TgM-A一样，除了高度碱性的电荷外，其尾部与任何其他肌球蛋白尾部都没有同源性。另一类非常规肌球蛋白的鉴定，包括肌球蛋白作为新的93 kDa TgM-A的结构，继续强调这个家庭的分子马达的多样性。(C)出版社：Academic Press Limited。
Here, we describe the complete deduced amino acid sequence of three unconventional myosins identified in the protozoan parasite Toxoplasma gondii. Phylogenetic analysis reveals that the three myosins represent a novel, highly-divergent class addition to the myosin superfamily. Toxoplasma gondii myosin-A (TgM-A) is a remarkably small approximate to 93 kDa myosin that shows a striking departure from typical myosin heavy chain structure in having a head and tail domain but no discernible neck domain. In other myosins, the neck is defined by one or more IQ motifs that serve as potential light chain binding domains. No IQ motifs are apparent in TgM-A. The tail domain of TgM-A encompasses only 57 amino acid residues and is characterized by its highly basic charge (pI = 10.8.) The other two Toxoplasma myosins, TgM-B and TgM-C appear to be the product of differential RNA splicing with TgM-B yielding a protein of approximate to 114 kDa and TgM-C a protein of approximate to 125 kDa. These two myosins are identical throughout their head domain and neck domain which contains a single IQ motif. TgM-B and C share the proximal 245 residues of their tail domain and then diverge in their tail structure distally. The tails, like that of TgM-A, share no homology to any other myosin tails apart from a highly basic charge. The identification of yet another class of unconventional myosins, including a myosin as novel in structure as the 93 kDa TgM-A, continues to underscore the diversity of this family of molecular motors. (C) 1997 Academic Press Limited.