Gibbs F E, Wilkinson M C, Rudland P S, Barraclough R
Department of Biochemistry, University of Liverpool, United Kingdom.
J Biol Chem. 1994 Jul 22;269(29):18992-9.
The S-100 proteins are a structurally related family displaying diverse intracellular and extracellular interactions. One such protein p9Ka (also known as calvasculin), or its mRNA (also known as CAPL, 42A, 18A2, mts, pEL 98), becomes elevated upon changes in the growth and differentiation of cells. Overexpression of p9Ka in benign rat mammary cells induces the metastatic phenotype. In order to help understand the role of p9Ka in these processes, the molecular properties of recombinant rat p9Ka have been studied. Recombinant p9Ka forms multimers in vitro, which are not due to intermolecular disulfide bridges, it binds 2 mol of calcium ions/mol of protein, and the binding of calcium ions is strongly antagonized by monovalent and divalent cations tested. Immunofluorescence studies indicate that p9Ka is located on cytoskeletal elements in a pattern which is identical to actin filaments stained with phalloidin. In vitro, it is shown that recombinant p9Ka binds to sites on at least two intracellular polypeptides. These sites display the same binding capacity for p9Ka in extracts of cultured rat mammary cells which show widely differing levels of expression of natural p9Ka. The results suggest that the production of p9Ka, and not of its target molecules, may be associated with the changes seen in cultured cells.
S-100蛋白是一个结构相关的蛋白家族，表现出多样的细胞内和细胞外相互作用。其中一种蛋白p9Ka（也称为钙血管素）或其mRNA（也称为CAPL、42A、18A2、mts、pEL 98）在细胞生长和分化发生变化时会升高。在良性大鼠乳腺细胞中过表达p9Ka会诱导转移表型。为了帮助理解p9Ka在这些过程中的作用，对重组大鼠p9Ka的分子特性进行了研究。重组p9Ka在体外形成多聚体，这不是由于分子间二硫键所致，它每摩尔蛋白质结合2摩尔钙离子，并且所测试的单价和二价阳离子会强烈拮抗钙离子的结合。免疫荧光研究表明，p9Ka以与用鬼笔环肽染色的肌动蛋白丝相同的模式位于细胞骨架成分上。在体外，已表明重组p9Ka与至少两种细胞内多肽上的位点结合。在培养的大鼠乳腺细胞提取物中，这些位点对p9Ka显示出相同的结合能力，而这些细胞提取物中天然p9Ka的表达水平差异很大。结果表明，p9Ka而非其靶分子的产生可能与培养细胞中观察到的变化有关。
