The cell walls of yeast cells possess a large mannan structure mainly comprising of a linear α1,6-linked mannose oligomer on the N-linked glycans. The biosynthesis of the mannan is initiated by ScOch1p α1,6-mannosyltransfease, and elongated by the mannan polymerase complexes M-Pol I and II in the Golgi of Saccharomyces cerevisiae. Here, we functionally characterized SpMnn9 and SpAnp1 proteins in the fission yeast Schizosaccharomyces pombe; these proteins are homologs of S. cerevisiae M-Pol II complex proteins ScMnn9p and ScAnp1p. Cells harboring disruptions in Spmnn9⁺ and Spanp1⁺ genes showed slower growth at 37°C and an increased sensitivity to hygromycin B, characteristic of a glycosylation defect. Results obtained from the acid phosphatase assay and high-performance liquid chromatography analysis of N-linked glycans in Spmnn9Δ and Spanp1Δ mutants suggested that the mannan structure in S. pombe is synthesized sequentially by the α-mannosyltransferases in the order of SpOch1p, SpMnn9p and SpAnp1p. Immunoprecipitation and split YFP analyses demonstrated that SpMnn9p and SpAnp1p form the M-Pol-II like complex. Together, these results provided an improved understanding of the mechanism of mannan synthesis by SpMnn9p and SpAnp1p in S. pombe.

酵母细胞的细胞壁具有大的甘露聚糖结构，主要由N-连接的聚糖上的线性α1,6-连接的甘露糖寡聚物组成。甘露聚糖的生物合成由Sc Och1pα1,6-甘露糖基转移酶引发，并由酿酒酵母高尔基体中的甘露聚糖聚合酶复合物M-Pol I和II延长。在这里，我们功能上裂殖酵母裂殖酵母中的Sp Mnn9和Sp Anp1蛋白的功能；这些蛋白是酿酒酵母M-Pol II复合蛋白Sc Mnn9p和Sc Anp1p的同源物。Spmnn9 ^+中具有破坏作用的细胞Spanp1 ⁺和Spanp1 ⁺基因在37°C时生长较慢，并且对潮霉素B（糖基化缺陷的特征）的敏感性增加。酸性磷酸酶测定和高效液相色谱分析Spmnn9Δ和Spanp1Δ突变体中N联聚糖的结果表明，粟酒裂殖酵母中的甘露聚糖结构由α-甘露糖基转移酶按Sp Och1p的顺序顺序合成，Sp Mnn9p和Sp Anp1p。免疫沉淀和YFP分裂分析表明Sp Mnn9p和SpAnp1p形成M-Pol-II样复合物。总之，这些结果提供了对S. pombe中Sp Mnn9p和Sp Anp1p甘露聚糖合成机理的更好理解。