Murthy S N, Liu T, Kaul R K, Köhler H, Steck T L
J Biol Chem. 1981 Nov 10;256(21):11203-8.
Band 3 is the predominant membrane-spanning polypeptide and the mediator of anion transport in the human erythrocyte. In addition, it provides the sites of association for fructose 1,6-bisphosphate aldolase and other cytoplasmic proteins with the membrane. The aldolase-binding activity of water-soluble fragments of band 3 was measured by their inhibition of aldolase catalytic activity and by their displacement of aldolase from ghosts. At saturation, the binding of one band 3 or certain of its fragments per aldolase molecule partially inhibited the catalytic activity and band 3 binding of the unliganded subunits of the tetramer through an apparently cooperative mechanism. An NH2-terminal 23,000-dalton fragment generated by S-cyanylation of the cytoplasmic pole of band 3 was approximately 20% as avid in binding aldolase as was native band 3. Several fragments cleaved from the NH2-terminal portion of the 23,000-dalton peptide by trypsin, mild acid hydrolysis, and cyanogen bromide digestion all bound aldolase, while fragments from the rest of the polypeptide were essentially inactive. The first 31 residues of band 3 contained 16 Asp plus Glu, no basic residues, and a blocked alpha-amino terminus. The highly acidic composition of this region is consistent with the strongly electrostatic character of the interaction between band 3 and aldolase, presumably at the strongly basic catalytic center of the enzyme. We conclude that the NH2-terminal region of band 3 bears the membrane-binding site for aldolase.
带3是人类红细胞中主要的跨膜多肽和阴离子转运的介质。此外，它还为果糖1,6 - 二磷酸醛缩酶和其他细胞质蛋白与膜的结合提供位点。通过对醛缩酶催化活性的抑制以及从血影中取代醛缩酶来测量带3水溶性片段的醛缩酶结合活性。在饱和状态下，每个醛缩酶分子结合一个带3或其某些片段会通过一种明显的协同机制部分抑制四聚体未结合配体亚基的催化活性和带3结合。通过对带3细胞质端进行S - 氰化反应产生的一个氨基末端23,000道尔顿的片段与醛缩酶结合的亲和力约为天然带3的20%。通过胰蛋白酶、温和酸水解和溴化氰消化从23,000道尔顿肽的氨基末端部分切割得到的几个片段都能结合醛缩酶，而多肽其余部分的片段基本无活性。带3的前31个残基包含16个天冬氨酸加谷氨酸，没有碱性残基，并且α - 氨基末端被封闭。该区域的高酸性组成与带3和醛缩酶之间相互作用的强静电特性一致，推测是在酶的强碱性催化中心处。我们得出结论，带3的氨基末端区域带有醛缩酶的膜结合位点。
