Sloan J, Kinghorn J R, Unkles S E
Department of Microbiology, Monash University, Clayton, Victoria 3168, Australia andSchool of Environmental and Evolutionary Biology, University of St Andrews, St Andrews, Fife KY16 9TH, UK.
Nucleic Acids Res. 1999 Feb 1;27(3):854-8. doi: 10.1093/nar/27.3.854.
Molybdoenzymes are ubiquitous and require a prosthetic group called the molybdenum cofactor for activity. We provide evidence here that the two heteromeric subunits (MOCO1-A and MOCO1-B) of human molybdopterin synthase, which is involved in the conversion of precursor Z to molybdopterin in the molybdenum cofactor biosynthetic pathway, are spe-cified by a single bicistronic mRNA with overlapping reading frames. The transcript is in low abundance and shows variable tissue distribution. We propose that leaky scanning of the first translational initiation codon for MOCO1-A by 40S ribosomal subunits occurs, allowing recognition of the AUG for the downstream MOCO1-B reading frame. Such a genetic arrangement may result in a constant ratio and close proximity of lowly expressed enzyme subunits which should, a priori, be especially advantageous for assembly in complex mammalian cells. The MOCO1 locus resides on human chromosome 5.
钼酶广泛存在，其活性需要一种称为钼辅因子的辅基。我们在此提供证据表明，人类钼蝶呤合酶的两个异源亚基（MOCO1-A和MOCO1-B）由具有重叠阅读框的单个双顺反子mRNA编码，该酶参与钼辅因子生物合成途径中前体Z向钼蝶呤的转化。该转录本丰度较低，且组织分布存在差异。我们推测，40S核糖体亚基对MOCO1-A的第一个翻译起始密码子进行了漏扫描，从而使得下游MOCO1-B阅读框的AUG能够被识别。这种基因排列可能导致低表达的酶亚基保持恒定比例并紧密相邻，从先验角度来看，这对于在复杂的哺乳动物细胞中进行组装尤为有利。MOCO1基因座位于人类5号染色体上。
