代谢产物活化蛋白(CAP、Catabolite activator protein)，也称为Camp接收蛋白，CRP)为一种转录活化剂，存在于溶剂中的同型二聚体；包含N端的配体键结区(CAPN，残基 1-138)，使蛋白形成二聚体，以及包含C端的DNA键结区(DBD, 残基 139-209)。 借由增加DNA蛋白的亲和性，使两个cAMP(环腺甘酸)分子键结于带有变构效应的负协同性和功能的CAP二聚体。当只有少量葡萄糖进入细胞中，则cAMP的浓度提升。 CAP有一种螺旋-转角-螺旋的结构，使他能成功键结于DNA的主要区位。两种螺旋互相加强，造成一个43°的转角结构，所以最后造成DNA 94°的转角。 这种情况使DNA分子打开，使RNA聚合酶可以键结上来，转译出乳糖分解的基因。cAMP-CAP对于乳糖操作子转录是必要的条件。 CAP主要功能为代谢产物的抑制，为一个典型的例子。

Catabolite Activator Protein (CAP; also known as cAMP receptor protein, CRP) is a transcriptional activator that exists as a homodimer in solution, with each subunit comprising a ligand-binding domain at the N-terminus (CAP, residues 1-138), which is also responsible for the dimerization of the protein, and a DNA-binding domain at the C-terminus (DBD, residues 139-209). Two cAMP (cyclic AMP) molecules bind dimeric CAP with negative cooperativity and function as allosteric effectors by increasing the protein's affinity for DNA. Cytosolic cAMP levels rise when the amount of glucose transported into the cell is low.