期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1978
卷号：75
期号：11
页码：5276-5280
DOI：10.1073/pnas.75.11.5276
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：X-ray diffraction studies to nominal resolutions of 3.0 A for unliganded aspartate carbamolytransferase (EC 2.1.3.2 )(R32 crystal symmetry) and of 2.8 A for the complex of aspartate carbamoyltransferase with cytidine triphosphate (P321 crystal symmetry) have yielded traces of the polypeptide chains of the catalytic (C) and regulatory (R) chains in the hexameric C6R6 molecules. The independent molecular structures of the liganded and unliganded forms of the enzyme are very nearly identical. In the regulatory chain there is a CTP-binding domain that interacts with an adjacent regulatory subunit and a zinc-binding domain that interacts with the catalytic subunit. In the catalytic chain a polar domain shows interactions between adjacent pairs of C chains to form each trimer C3 while an equatorial domain shows intramolecular C3--C3 interactions. The active site is at or near the interface between adjacent C chains within the trimers. Probably each active center involves amino acid residues from adjacent C chains.
