Tolmasky D S, Krisman C R
Instituto de Investigaciones Bioquímicas Luis F. Leloir, Fundación Campomar, Facultad de Ciencias Exactas y Naturales, U.B.A., CONICET, Argentina.
Cell Mol Biol (Noisy-le-grand). 1996 Jul;42(5):589-98.
The sequence of glucosylation steps from "genesine", the naked initiation protein, to rat heart glycogen are described. During a pulse experiment with UDP-14C-glucose the radiolabelled 14C-glucosylated protein band of 38 and 42 kDa appeared first. Mn+2 stimulates the first transfer of glucoses to "genesine" and the 38 kDa and 42 kDa protein bands appear. Although further growth is inhibited by Mn+2, this inhibition is reversed by PMSF+Glc6P. In the absence of Mn+2, a major 14C-glucosylated protein band of 60 kDa and also a faint one in the location of 42 kDa appeared. Designing the synthetic and degradative processes it is possible to go from the 42 kDa 14C-glucosylated protein band through species of higher mw to glycogen and back to the 42 kDa one. In the "genesine" autoglucosylating process involved in the initiation of rat heart biogenesis, several dissimilar activities had to be distinguished. The first glycogen initiator 1 (GI1) is that with an activity stimulated by Mn+2 which transfers one or two glucoses. The other glycogen initiator 2 (GI2) is inhibited by Mn+2 and in its absence produces a glucosylated protein band of 60 kDa. Finally a third one, stimulated by Glc6P, we named it Elongator 1 (E1), which in the presence of mumolar concentration of UDPGlc originates a family of glucosylated protein bands almost from 42 kDa to 200 kDa.
描述了从无修饰起始蛋白“肌苷”到大鼠心脏糖原的糖基化步骤序列。在用UDP-14C-葡萄糖进行的脉冲实验中，首先出现了放射性标记的38 kDa和42 kDa的14C-糖基化蛋白条带。Mn+2刺激葡萄糖首次转移至“肌苷”，并出现38 kDa和42 kDa的蛋白条带。尽管Mn+2会抑制进一步的生长，但PMSF + Glc6P可逆转这种抑制作用。在没有Mn+2的情况下，出现了一条主要的60 kDa的14C-糖基化蛋白条带以及一条位于42 kDa位置的微弱条带。通过设计合成和降解过程，有可能从42 kDa的14C-糖基化蛋白条带经过分子量更高的物种直至糖原，然后再回到42 kDa的条带。在大鼠心脏生物合成起始过程中涉及的“肌苷”自糖基化过程中，必须区分几种不同的活性。第一个糖原起始因子1（GI1）是其活性受Mn+2刺激的因子，可转移一或两个葡萄糖。另一个糖原起始因子2（GI2）受Mn+2抑制，在没有Mn+2的情况下会产生一条60 kDa的糖基化蛋白条带。最后，第三个受Glc6P刺激，我们将其命名为延伸因子1（E1），在存在微摩尔浓度的UDPGlc时，它会产生一系列几乎从42 kDa到200 kDa的糖基化蛋白条带。
