Navaratnam N, Fujino T, Bayliss J, Jarmuz A, How A, Richardson N, Somasekaram A, Bhattacharya S, Carter C, Scott J
MRC Molecular Medicine Group, Imperial College School of Medicine, Hammersmith Hospital, London, UK.
J Mol Biol. 1998 Jan 30;275(4):695-714. doi: 10.1006/jmbi.1997.1506.
ApoB RNA-editing enzyme (APOBEC-1) is a cytidine deaminase. Molecular modeling and mutagenesis show that APOBEC-1 is related in quaternary and tertiary structure to Escherichia coli cytidine deaminase (ECCDA). Both enzymes form a homodimer with composite active sites constructed with contributions from each monomer. Significant gaps are present in the APOBEC-1 sequence, compared to ECCDA. The combined mass of the gaps (10 kDa) matches that for the minimal RNA substrate. Their location in ECCDA suggests how APOBEC-1 can be reshaped to accommodate an RNA substrate. In this model, the asymmetrical binding to one active site of a downstream U (equivalent to the deamination product) helps target the other active site for deamination of the upstream C substrate.
载脂蛋白B RNA编辑酶（APOBEC-1）是一种胞苷脱氨酶。分子建模和诱变研究表明，APOBEC-1在四级和三级结构上与大肠杆菌胞苷脱氨酶（ECCDA）相关。这两种酶均形成同型二聚体，其复合活性位点由每个单体共同构成。与ECCDA相比，APOBEC-1序列中存在明显的缺口。这些缺口的总质量（10 kDa）与最小RNA底物的质量相匹配。它们在ECCDA中的位置提示了APOBEC-1如何重塑以容纳RNA底物。在该模型中，与下游U（等同于脱氨产物）的一个活性位点的不对称结合有助于将另一个活性位点靶向用于上游C底物的脱氨。
