Hirsch H H, Schiffer H H, Wolf D H
Institut für Medizinische Mikrobiologie, Universität Basel, Switzerland.
Eur J Biochem. 1992 Aug 1;207(3):867-76. doi: 10.1111/j.1432-1033.1992.tb17118.x.
The vacuolar proteinase yscB (PrB) has been implicated in the final maturation of procarboxypeptidase yscY (pro-CpY) to the mature wild-type form CpYb of 61 kDa. In PrB-deficient mutants, only the proteinase yscA processed form CpYa of 62 kDa is found [Mechler, B., Müller, H. & Wolf, D. H. (1987) EMBO J. 6, 2157-2163]. We report now that, akin to CpY, two forms of mature proteinase yscA (PrA) can be distinguished. In PrB-deficient mutant cells, PrAa, migrating at about 43 kDa in SDS/PAGE, is found, whereas PrAb, found in wild-type cells, had the known molecular mass of 42 kDa. In the PrB-deficient strain, pro-PrA and pro-CpY matured only to the higher-molecular-mass forms, PrAa and CpYa, and the maturation of both precursors was slower than in the isogenic wild-type strain. Pulse-labeling experiments indicated that the mature forms, PrAb or CpYb, are generated directly in the PrB-containing wild-type strain in vivo. In vitro experiments showed that PrB is able to trigger maturation of its 42-kDa pro-PrB precursor to mature PrB in the absence of PrA. Mature PrB and its proteolytic activity, however, shows a higher stability in the presence of mature PrA. The data indicate a molecular and kinetic participation of proteinase yscB in vacuolar hydrolase precursor maturation.
液泡蛋白酶yscB（PrB）被认为与羧肽酶原yscY（pro-CpY）最终成熟为61 kDa的成熟野生型形式CpYb有关。在PrB缺陷型突变体中，仅发现蛋白酶yscA加工形成的62 kDa的CpYa [Mechler, B., Müller, H. & Wolf, D. H. (1987) EMBO J. 6, 2157 - 2163]。我们现在报告，类似于CpY，可以区分成熟蛋白酶yscA（PrA）的两种形式。在PrB缺陷型突变体细胞中，发现了在SDS/PAGE中迁移约43 kDa的PrAa，而在野生型细胞中发现的PrAb具有已知的42 kDa分子量。在PrB缺陷型菌株中，前体PrA和前体CpY仅成熟为高分子量形式PrAa和CpYa，并且两种前体的成熟都比同基因野生型菌株慢。脉冲标记实验表明，成熟形式PrAb或CpYb在体内含PrB的野生型菌株中直接产生。体外实验表明，在没有PrA的情况下，PrB能够触发其42 kDa的前体PrB成熟为成熟的PrB。然而，在成熟PrA存在的情况下，成熟PrB及其蛋白水解活性表现出更高的稳定性。数据表明蛋白酶yscB在液泡水解酶前体成熟中具有分子和动力学参与。
