Brownlee A G, Phillips D R, Polya G M
Eur J Biochem. 1980 Aug;109(1):39-49. doi: 10.1111/j.1432-1033.1980.tb04765.x.
Two high-affinity cAMP-binding proteins (I and II) have been purified to homogeneity from baker's yeast by a procedure avoiding proteolytic damage. These proteins have been identified as multiple forms of glyceraldehyde-3-phosphate dehydrogenase. The two cAMP-binding proteins are similar in affinities for cAMP, have identical elution volumes on gel filtration, and contain one type of subunit (Mr 37 500). The form II of glyceraldehyde-3-phosphate dehydrogenase is free of NAD+ and has a Kd of 1.3 X 10(-6) M with respect to cAMP. A marked concentration-dependent self-association of the subunits of the form-II protein was revealed by Yphantis sedimentation equilibrium studies. Significant monomer concentrations are present at total concentrations less than 0.02 mg/ml. Conventional sedimentation equilibrium analyses indicated a tetramer Mr of 170 000. The high-affinity binding of cAMP to glyceraldehyde-3-phosphate dehydrogenase may significantly reduce intracellular cAMP levels and is also discussed in relation to the nature of eukaryote cAMP-binding proteins with similar native or subunit Mr values which are at present functionally undefined.
通过避免蛋白水解损伤的方法，已从面包酵母中纯化出两种高亲和力的环磷酸腺苷（cAMP）结合蛋白（I和II），达到了均一性。这些蛋白已被鉴定为甘油醛-3-磷酸脱氢酶的多种形式。这两种cAMP结合蛋白对cAMP的亲和力相似，在凝胶过滤中的洗脱体积相同，且含有一种亚基（相对分子质量37500）。甘油醛-3-磷酸脱氢酶的II型不含烟酰胺腺嘌呤二核苷酸（NAD+），对cAMP的解离常数（Kd）为1.3×10⁻⁶ M。扬凡蒂斯沉降平衡研究揭示了II型蛋白亚基明显的浓度依赖性自缔合。在总浓度低于0.02 mg/ml时存在显著的单体浓度。传统的沉降平衡分析表明四聚体的相对分子质量为170000。cAMP与甘油醛-3-磷酸脱氢酶的高亲和力结合可能会显著降低细胞内cAMP水平，并且还结合目前功能尚未明确的、具有相似天然或亚基相对分子质量值的真核生物cAMP结合蛋白的性质进行了讨论。
