Longoni S, James P, Chiesi M
Department of Pharmaceutical Research, Ciba-Geigy, Basel, Switzerland.
Mol Cell Biochem. 1990 Dec 3;99(1):113-20.
A water soluble protein, a major component of the cytosolic fraction of rat heart cells, was purified using either reverse phase HPLC or antibodies affinity chromatography procedures and characterized. The protein has an apparent Mr of 24 k, as judged by SDS-gel electrophoresis. Under non-denaturing conditions, however, the protein occurs as a homomultimer (Mr between 400 and 650 k) of the monomeric 24 kDa species and could be selectively enriched by fractionation of the cytosolic fraction on 10 to 40% sucrose gradients. Polyclonal antibodies, raised against the denatured 24 kDa protein, were used to investigate its tissue distribution. Besides the heart, where it is very abundant, the 24 kDa protein is expressed also in other red muscles and in kidneys, but was not detectable in stomach, thymus, liver, and brain. The amino acid composition of the protein and the partial amino acid sequence of various proteolytic fragments was determined. A search for homologies of the primary structure of known proteins has shown that the 24 kDa protein is strikingly similar, if not identical to alpha-B-crystallin. In fact, the two proteins were found to be indistinguishable also by immunological criteria. This study demonstrates that the lens protein alpha B-crystallin is a major cytosolic component of heart cells.
一种水溶性蛋白质是大鼠心脏细胞胞质部分的主要成分，采用反相高效液相色谱法或抗体亲和层析法进行纯化并表征。通过SDS-凝胶电泳判断，该蛋白质的表观分子量为24kDa。然而，在非变性条件下，该蛋白质以24kDa单体的同多聚体形式存在（分子量在400至650k之间），并且可以通过在10%至40%的蔗糖梯度上对胞质部分进行分级分离来选择性富集。针对变性的24kDa蛋白质制备的多克隆抗体用于研究其组织分布。除了在心脏中含量非常丰富外，24kDa蛋白质在其他红色肌肉和肾脏中也有表达，但在胃、胸腺、肝脏和大脑中未检测到。测定了该蛋白质的氨基酸组成以及各种蛋白水解片段的部分氨基酸序列。对已知蛋白质一级结构的同源性搜索表明，24kDa蛋白质与α-B-晶状体蛋白极为相似，甚至可以说是相同的。事实上，通过免疫学标准也发现这两种蛋白质难以区分。这项研究表明，晶状体蛋白αB-晶状体蛋白是心脏细胞的主要胞质成分。
