Scherer S, Potts M
Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg 24061.
J Biol Chem. 1989 Jul 25;264(21):12546-53.
A desiccation-tolerant cyanobacterium Nostoc commune accumulates a novel group of acidic proteins when colonies are subjected to repeated cycles of drying and rehydration. The proteins occur in high concentrations; they have isoelectric points between 4.3 and 4.8 and apparent molecular masses between 30 and 39 kDa. The purification of three of these proteins with molecular masses of 33, 37, and 39 kDa is described. The amino-terminal sequence of the 39-kDa protein is Ala-Leu-Tyr-Gly-Tyr-Thr-Ile-Gly-Glu. Peptide mapping of the 39- and the 33-kDa proteins, using different protease, gave similar patterns of digestion fragments. The amino acid compositions of the proteins isolated were similar, and each cross-reacted with a polyclonal antibody raised against the largest (39-kDa) protein. The results indicate that the microheterogeneity observed was generated by in vivo proteolysis of the 39-kDa protein. It is suggested that this protein is a water stress protein with a protective function on a structural level.
一种耐干燥的蓝藻普通念珠藻（Nostoc commune）在菌落经历反复的干燥和复水循环时会积累一组新的酸性蛋白质。这些蛋白质浓度很高；它们的等电点在4.3至4.8之间，表观分子量在30至39 kDa之间。本文描述了其中三种分子量分别为33、37和39 kDa的蛋白质的纯化过程。39 kDa蛋白质的氨基末端序列为Ala-Leu-Tyr-Gly-Tyr-Thr-Ile-Gly-Glu。使用不同蛋白酶对39 kDa和33 kDa蛋白质进行肽图谱分析，得到了相似的消化片段模式。分离得到的蛋白质的氨基酸组成相似，并且每种蛋白质都与针对最大的（39 kDa）蛋白质产生的多克隆抗体发生交叉反应。结果表明，观察到的微异质性是由39 kDa蛋白质的体内蛋白水解产生的。有人认为这种蛋白质是一种水分胁迫蛋白，在结构水平上具有保护功能。
