An unanticipated architecture of the 750-kDa α6β6 holoenzyme of 3-methylcrotonyl-CoA carboxylase.
An unanticipated architecture of the 750-kDa α6β6 holoenzyme of 3-methylcrotonyl-CoA carboxylase.
复制标题
DOI：
10.1038/nature10691
复制
发表时间：
2011-12-11
期刊：
影响因子：
64.8
通讯作者：
Tong L
中科院分区：
文献类型：
--
作者：
Huang CS;Ge P;Zhou ZH;Tong L
3-甲基巴豆酰-CoA羧化酶（MCC）是生物素依赖性羧化酶超家族的成员，对于亮氨酸的代谢是必需的，并且该酶的缺陷突变与甲基巴豆酰甘氨酸尿症（MCG）和人类中的其它严重疾病相关。MCC与丙酰辅酶A羧化酶（PCC）具有很强的序列保守性，两者的全酶均为750 kD的α6β6十二聚体。因此，MCC全酶的结构预计与PCC的结构高度相似。在这里，我们报告了铜绿假单胞菌MCC（PaMCC）全酶单独和与辅酶A复合的晶体结构。令人惊讶的是，这些结构表明，与PCC相比，PaMCC的结构和整体形状明显不同。PaMCC全酶中的α亚基表现出三聚体结合，而PCC中的α亚基相互之间没有接触。此外，PaMCC中β亚基中的两个结构域的位置相对于PCC中的那些互换。这些结构信息为理解MCC致病突变奠定了基础，并为生物素依赖性羧化酶的催化机制和进化提供了新的见解。MCC和PCC之间的巨大结构差异也对序列保守性和结构相似性之间的关系具有普遍意义。
3-methylcrotonyl-CoA carboxylase (MCC), a member of the biotin-dependent carboxylase superfamily, is essential for the metabolism of leucine, and deficient mutations in this enzyme are linked to methylcrotonylglycinuria (MCG) and other serious diseases in humans . MCC has strong sequence conservation with propionyl-CoA carboxylase (PCC), and their holoenzymes are both 750 kD α6β6 dodecamers. Therefore the architecture of the MCC holoenzyme is expected to be highly similar to that of PCC . Here we report the crystal structures of the Pseudomonas aeruginosa MCC (PaMCC) holoenzyme, alone and in complex with coenzyme A. Surprisingly, the structures show that the architecture and overall shape of PaMCC are strikingly different when compared to PCC. The α subunits display trimeric association in the PaMCC holoenzyme while they have no contacts with each other in PCC. Moreover, the positions of the two domains in the β subunit in PaMCC are swapped relative to those in PCC. The structural information establishes a foundation for understanding the disease-causing mutations of MCC and provides new insights into the catalytic mechanism and evolution of biotin-dependent carboxylases. The large structural differences between MCC and PCC also have general implications for the relationship between sequence conservation and structural similarity.