Anion exchanger 1 (AE1) is a 95 kDa glycoprotein that facilitates exchange across the erythrocyte plasma membrane. This transport activity resides in the 52 kDa C-terminal membrane domain (Gly³⁶¹-Val⁹¹¹) predicted to span the membrane 14 times. To explore the role of tryptophan (Trp) residues in AE1 function, the seven endogenous Trp residues in the membrane domain were mutated individually to alanine (Ala) and phenylalanine (Phe). Expression levels, cell surface abundance, inhibitor binding and transport activities of the mutants were measured upon expression in HEK-293 cells. The seven Trp residues divided into three classes according the impact of mutations on the functional expression of AE1: Class 1, dramatically decreased expression (Trp⁴⁹² and Trp⁴⁹⁶); Class 2, decreased expression by Ala substitution but not Phe (Trp⁶⁴⁸, Trp⁶⁶² and Trp⁷²³); and Class 3, normal expression (Trp⁸³¹ and Trp⁸⁴⁸). The results indicate that Trp residues play differential roles in AE1 expression and function depending on their location in the protein and that Trp mutants with low expression are misfolded and retained in the endoplasmic reticulum.

阴离子交换剂1（AE1）是一种95 kDa的糖蛋白，可促进 跨红细胞质膜交换。该转运活性存在于52kDa的C端膜结构域（Gly ³⁶¹ -Val ⁹¹¹）中，预计其跨膜14倍。为了探索色氨酸（Trp）残基在AE1功能中的作用，将膜结构域中的七个内源性Trp残基分别突变为丙氨酸（Ala）和苯丙氨酸（Phe）。在HEK-293细胞中表达后，测量突变体的表达水平，细胞表面丰度，抑制剂结合和转运活性。根据突变对AE1功能表达的影响，七个Trp残基分为三类：1类，表达急剧下降（Trp ⁴⁹²和Trp ⁴⁹⁶）; 第2类，通过Ala取代而不是Phe降低表达（Trp ⁶⁴⁸，Trp ⁶⁶²和Trp ⁷²³）；和3类，正则表达式（Trp ⁸³¹和Trp ⁸⁴⁸）。结果表明，Trp残基在AE1表达和功能中起着不同的作用，具体取决于它们在蛋白质中的位置，而低表达的Trp突变体被错误折叠并保留在内质网中。