Structural organization of the multifunctional animal fatty-acid synthase.
Structural organization of the multifunctional animal fatty-acid synthase.
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DOI：
10.1111/j.1432-1033.1991.tb16052.x
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发表时间：
1991-06
期刊：
影响因子：
--
通讯作者：
A. Witkowski;V. Rangan;Z. Randhawa;C. Amy;S. Smith
中科院分区：
文献类型：
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作者：
A. Witkowski;V. Rangan;Z. Randhawa;C. Amy;S. Smith
多功能脂肪酸合成酶的氨基酸序列已被检查，以调查的七个功能域的确切位置。使用三种独立的方法获得了良好的协议在预测的区域间边界的位置。首先，有限的蛋白水解攻击，产生相对稳定的，大的多肽片段的网站进行了鉴定，隐蔽的网站蛋白酶攻击的亚基界面被揭露，首先解离成其组成亚基的二聚体。第二，鉴定了表现出高于平均水平的非保守突变率的多肽区域。第三，推定的功能结构域的大小进行了比较，表现出类似的一级或二级结构的相关单功能蛋白质。残基1-406归属于氧代酰基合酶，残基430-802归属于丙二酰/乙酰基转移酶，残基1630-1850归属于烯酰还原酶，残基1870-2100归属于氧化还原酶，残基2114-2190归属于酰基载体蛋白，残基2200-2505归属于硫酯酶。47-kDa的转移酶和8-kDa的酰基载体蛋白结构域，这是位于多功能亚基的两端，然而，从胰蛋白酶消化酶作为一个非共价相关的复合物分离。此外，将包含残基1160-1545的位于中心的结构域分离为带切口的二聚体。这些研究结果表明，头到尾并列的亚基之间的相互作用发生在极地和赤道地区，是一致的，与以前派生的电子显微图像，显示在这些地区的亚基接触。该数据允许细化的脂肪酸合成酶二聚体的模型，并建议丙二酰/乙酰转移酶和oxoacyl合酶的一个亚基合作的还原酶，酰基载体蛋白和硫酯酶的伴侣亚基中形成一个中心的脂肪酸合成。
The amino acid sequence of the multifunctional fatty-acid synthase has been examined to investigate the exact location of the seven functional domains. Good agreement in predicting the location of interdomain boundaries was obtained using three independent methods. First, the sites of limited proteolytic attack that give rise to relatively stable, large polypeptide fragments were identified; cryptic sites for protease attack at the subunit interface were unmasked by first dissociating the dimer into its component subunits. Second, polypeptide regions exhibiting higher-than-average rates of non-conservative mutation were identified. Third, the sizes of putative functional domains were compared with those of related monofunctional proteins that exhibit similar primary or secondary structure. Residues 1-406 were assigned to the oxoacyl synthase, residues 430-802 to the malonyl/acetyl transferase, residues 1630-1850 to the enoyl reductase, residues 1870-2100 to the oxyreductase, residues 2114-2190 to the acyl-carrier protein and residues 2200-2505 to the thioesterase. The 47-kDa transferase and 8-kDa acyl-carrier-protein domains, which are situated at opposite ends of the multifunctional subunit, were nevertheless isolated from tryptic digests as a non-covalently associated complex. Furthermore, a centrally located domain encompassing residues 1160-1545 was isolated as a nicked dimer. These findings, indicating that interactions between the head-to-tail juxtaposed subunits occur in both the polar and equatorial regions, are consistent with previously derived electron-micrograph images that show subunit contacts in these areas. The data permit refinement of the model for the fatty-acid synthase dimer and suggest that the malonyl/acetyl transferase and oxoacyl synthase of one subunit cooperate with the reductases, acyl carrier protein and thioesterase of the companion subunit in the formation of a center for fatty-acid synthesis.