Faure M, Camonis J H, Jacquet M
Laboratoires de Biologie Expérimentale, Université Paris-Sud.
Eur J Biochem. 1989 Feb 1;179(2):345-58. doi: 10.1111/j.1432-1033.1989.tb14560.x.
We have isolated and characterized a Dictyostelium discoideum gene (PYR1-3) encoding a multifunctional protein that carries the three first enzymatic activities of the de novo pyrimidine biosynthetic pathway. The PYR1-3 gene is adjacent to another gene of the pyrimidine biosynthetic pathway (PYR4); the two genes are separated by a 1.5-kb non-coding sequence and transcribed divergently. The PYR1-3 gene is transcribed to form a 7.5-kb polyadenylated mRNA. As with the other genes of the pyrimidine biosynthetic pathway, the PYR1-3 mRNA level is high during growth and decreases sharply during development. We have determined the nucleotide sequence of 63% of the coding region of the PYR1-3 gene. We have identified the activities of the protein encoded by the D. discoideum PYR1-3 gene by comparison of amino acid sequences with the products of genes of known function. The PYR1-3 gene contains four distinct regions that probably correspond to four domains in the protein. From the NH2 extremity to the COOH extremity, these domains are: glutamine amidotransferase, carbamoylphosphate synthetase, dihydroorotase and aspartate transcarbamylase. This organization is identical to the one found in the rudimentary gene of Drosophila. The evolutionary implications of this finding are discussed.
我们已经分离并鉴定了一种盘基网柄菌基因（PYR1-3），该基因编码一种多功能蛋白质，它具有从头嘧啶生物合成途径的前三种酶活性。PYR1-3基因与嘧啶生物合成途径的另一个基因（PYR4）相邻；这两个基因被一个1.5kb的非编码序列隔开，并以相反方向转录。PYR1-3基因转录形成一个7.5kb的多聚腺苷酸化mRNA。与嘧啶生物合成途径的其他基因一样，PYR1-3 mRNA水平在生长期间较高，而在发育期间急剧下降。我们已经确定了PYR1-3基因63%编码区的核苷酸序列。通过将氨基酸序列与已知功能基因的产物进行比较，我们确定了盘基网柄菌PYR1-3基因编码的蛋白质的活性。PYR1-3基因包含四个不同的区域，可能对应于该蛋白质的四个结构域。从氨基末端到羧基末端，这些结构域依次为：谷氨酰胺酰胺转移酶、氨甲酰磷酸合成酶、二氢乳清酸酶和天冬氨酸转氨甲酰酶。这种结构与在果蝇的rudimentary基因中发现的结构相同。本文讨论了这一发现的进化意义。
