Staneva Dessislava, Uccelletti Daniela, Farina Francesca, Venkov Pencho, Palleschi Claudio
Department of Molecular Genetics, Institute of Molecular Biology, Bulgarian Academy of Sciences, Sofia 1113, Bulgaria.
Yeast. 2004 Jan 15;21(1):41-51. doi: 10.1002/yea.1055.
Phosphomannomutase (PMM) is a key enzyme, which catalyses one of the first steps in the glycosylation pathway, the conversion of D-mannose-6-phosphate to D-mannose-1-phosphate. The latter is the substrate for the synthesis of GDP-mannose, which serves as the mannosyl donor for the glycosylation reactions in eukaryotic cells. In the yeast Saccharomyces cerevisiae PMM is encoded by the gene SEC53 (ScSEC53) and the deficiency of PMM activity leads to severe defects in both protein glycosylation and secretion. We report here on the isolation of the Kluyveromyces lactis SEC53 (KlSEC53) gene from a genomic library by virtue of its ability to complement a Saccharomyces cerevisiae sec53 mutation. The sequenced DNA fragment contained an open reading frame of 765 bp, coding for a predicted polypeptide, KlSec53p, of 254 amino acids. The KlSec53p displays a high degree of homology with phosphomannomutases from other yeast species, protozoans, plants and humans. Our results have demonstrated that KlSEC53 is the functional homologue of the ScSEC53 gene. Like ScSEC53, the KlSEC53 gene is essential for K. lactis cell viability. Phenotypic analysis of a K. lactis strain overexpressing the KlSEC53 gene revealed defects expected for impaired cell wall integrity.
磷酸甘露糖变位酶（PMM）是一种关键酶，它催化糖基化途径中的第一步反应，即将D-甘露糖-6-磷酸转化为D-甘露糖-1-磷酸。后者是合成GDP-甘露糖的底物，而GDP-甘露糖是真核细胞中糖基化反应的甘露糖基供体。在酿酒酵母中，PMM由SEC53基因（ScSEC53）编码，PMM活性的缺乏会导致蛋白质糖基化和分泌出现严重缺陷。我们在此报告，通过其互补酿酒酵母sec53突变的能力，从基因组文库中分离出乳酸克鲁维酵母SEC53（KlSEC53）基因。测序的DNA片段包含一个765 bp的开放阅读框，编码一个预测的由254个氨基酸组成的多肽KlSec53p。KlSec53p与来自其他酵母物种、原生动物、植物和人类的磷酸甘露糖变位酶具有高度同源性。我们的结果表明，KlSEC53是ScSEC53基因的功能同源物。与ScSEC53一样，KlSEC53基因对乳酸克鲁维酵母的细胞活力至关重要。对过表达KlSEC53基因的乳酸克鲁维酵母菌株进行的表型分析揭示了预期的细胞壁完整性受损的缺陷。
