Clancey C J, Chang S C, Dowhan W
Department of Biochemistry and Molecular Biology, University of Texas Medical School, Houston 77225.
J Biol Chem. 1993 Nov 25;268(33):24580-90.
A gene (PSD1) encoding a phosphatidylserine decarboxylase of Saccharomyces cerevisiae was cloned by complementation of a conditional lethal mutation in the homologous gene in Escherichia coli strain EH150. Expression of the cDNA clone in EH150 corrected growth, phospholipid, and phosphatidylserine decarboxylase activity defects. Expression of the genomic clone in wild type yeast resulted in 20-fold amplification of phosphatidylserine decarboxylase activity. A 1500-base pair open reading frame encodes a 56,558-Da protein with a potential mitochondrial targeting sequence. Upstream regulatory elements found in other enzymes of the phospholipid biosynthetic pathway are present in PSD1. The derived amino acid sequence shows 44 and 35% identity with the phosphatidylserine decarboxylases from Chinese hamster ovary cells and E. coli, respectively. Near the carboxyl terminus is an LGST sequence which, in E. coli, is the site of proteolytic cleavage of the proenzyme into the alpha and beta subunits and formation of the pyruvate prosthetic group (Dowhan, W., and Li, Q.-X. (1992) Methods Enzymol. 209, 348-359). Disruption of the PSD1 gene in a haploid strain of yeast resulted in loss of detectable decarboxylase activity but little alteration of the growth properties or phospholipid composition. These results suggest that yeast has a second phosphatidylserine decarboxylation activity.
通过互补大肠杆菌菌株EH150中同源基因的条件致死突变，克隆了编码酿酒酵母磷脂酰丝氨酸脱羧酶的基因（PSD1）。cDNA克隆在EH150中的表达纠正了生长、磷脂和磷脂酰丝氨酸脱羧酶活性缺陷。基因组克隆在野生型酵母中的表达导致磷脂酰丝氨酸脱羧酶活性扩增20倍。一个1500个碱基对的开放阅读框编码一个56558道尔顿的蛋白质，带有一个潜在的线粒体靶向序列。磷脂生物合成途径中其他酶的上游调控元件也存在于PSD1中。推导的氨基酸序列与中国仓鼠卵巢细胞和大肠杆菌的磷脂酰丝氨酸脱羧酶分别有44%和35%的同一性。在羧基末端附近是一个LGST序列，在大肠杆菌中，该序列是前体酶蛋白水解切割成α和β亚基以及丙酮酸辅基形成的位点（Dowhan, W., and Li, Q.-X. (1992) Methods Enzymol. 209, 348 - 359）。酵母单倍体菌株中PSD1基因的破坏导致可检测的脱羧酶活性丧失，但生长特性或磷脂组成几乎没有改变。这些结果表明酵母具有第二种磷脂酰丝氨酸脱羧活性。
