TROPOMYOSIN IS ESSENTIAL IN YEAST, YET THE TPM1 AND TPM2 PRODUCTS PERFORM DISTINCT FUNCTIONS
TROPOMYOSIN IS ESSENTIAL IN YEAST, YET THE TPM1 AND TPM2 PRODUCTS PERFORM DISTINCT FUNCTIONS
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DOI：
10.1083/jcb.128.3.383
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发表时间：
1995-02-01
影响因子：
7.8
通讯作者：
BRETSCHER, A
中科院分区：
文献类型：
--
作者：
DREES, B;BROWN, C;BRETSCHER, A
酿酒酵母第九号染色体的序列分析揭示了一个由166个残基组成的开放阅读框，被命名为TPM2，它与编码酵母中主要原肌球蛋白形式的TPM1具有64.5%的序列同一性。对Tpm2p的纯化和特性分析表明，它是一种具有真正原肌球蛋白特征的蛋白质；它在体内的含量约为Tpm1p的六分之一。生化和序列分析表明，Tpm2p沿着肌动蛋白丝跨越4个肌动蛋白单体，而Tpm1p跨越5个。尽管Tpm2p长度较短，但它可以与Tpm1p竞争结合F - 肌动蛋白。体内Tpm2p的过表达使单倍体的轴向出芽转变为双极模式，并且这种情况可以通过Tpm1p的共同过表达而部分被抑制。这表明这两种原肌球蛋白具有不同的功能，并且它们之间的比例对于正确的形态发生很重要。在其他方面为野生型的细胞中，Tpm2p的缺失没有可检测到的表型，但与tpmlΔ组合时是致死的。Tpm2p的过表达不能抑制与tpmlΔ相关的生长或细胞表面靶向缺陷，因此这两种原肌球蛋白必须执行一种基本功能，但在功能上不可互换。因此，酿酒酵母为研究两种具有不同但又重叠功能的原肌球蛋白提供了一个简单的系统。
Sequence analysis of chromosome IX of Saccharomyces cerevisiae revealed an open reading frame of 166 residues, designated TPM2, having 64.5% sequence identity to TPM1, that encodes the major form of tropomyosin in yeast. Purification and characterization of Tpm2p revealed a protein with the characteristics of a bona fide tropomyosin; it is present in vivo at about one sixth the abundance of Tpm1p. Biochemical and sequence analysis indicates that Tpm2p spans four actin monomers along a filament, whereas Tpm1p spans five. Despite its shorter length, Tpm2p can compete with Tpm1p for binding to F-actin. Over-expression of Tpm2p in vivo alters the axial budding of haploids to a bipolar pattern, and this can be partially suppressed by co-overexpression of Tpm1p. This suggests distinct functions for the two tropomyosins, and indicates that the ratio between them is important for correct morphogenesis. Loss of Tpm2p has no detectable phenotype in otherwise wild type cells, but is lethal in combination with tpml Delta. Over-expression of Tpm2p does not suppress the growth or cell surface targeting defects associated with tpml Delta, so the two tropomyosins must perform an essential function, yet are not functionally interchangeable. S. cerevisiae therefore provides a simple system for the study of two tropomyosins having distinct yet overlapping functions.