Kogan G L, Gvozdev V A
Mol Biol (Mosk). 2014 Mar-Apr;48(2):223-31.
The functions of the evolutionary conservative complex NAC (Nascent polypepetide Associated Complex) and its subunits are discussed. The heterodimeric NAC protein contains alpha- and beta-subunits and is found to be reversibly bounded to the ribosome in all eukaryotes, from yeast to humans. NAC contacts the nascent polypeptide and protects it from proteolysis. NAC participates in polypeptide chain folding and modulates protein secretion and transmembrane protein formation. Mutations and deletions of genes, encoding NAC subunits are lethal in early development of multicellular eukaryotes. NAC is involved in the ribosome biogenesis. The beta-subunit interacts with caspase-3 and may be involved in the regulation of the apoptotic pathway. The variants of NAC proteins can be considered as chaperone complexes, involved in the response of the cell and the organism to stress factors, as well as regulators of apoptosis. The genes encoding beta-subunits are rapidly evolved, their duplications cause the formation of tissue specific beta-subunit variants with a different number of putative caspase cleavage sites. The homodimer of alpha-subunits is shown to be the RNA/DNA binding protein and acts as a transcriptional cofactor. The diversity in the functioning of NAC is a prime example of a protein that performs a variety of biological functions (moonlighting protein).
本文讨论了进化保守复合物新生多肽相关复合物（NAC）及其亚基的功能。异二聚体NAC蛋白包含α亚基和β亚基，在从酵母到人类的所有真核生物中均被发现可与核糖体可逆结合。NAC与新生多肽接触并保护其免受蛋白水解。NAC参与多肽链折叠，并调节蛋白质分泌和跨膜蛋白形成。编码NAC亚基的基因突变和缺失在多细胞真核生物的早期发育中是致命的。NAC参与核糖体生物合成。β亚基与半胱天冬酶-3相互作用，可能参与凋亡途径的调控。NAC蛋白的变体可被视为伴侣复合物，参与细胞和生物体对应激因子的反应，以及凋亡的调节因子。编码β亚基的基因快速进化，其复制导致形成具有不同数量假定半胱天冬酶切割位点的组织特异性β亚基变体。α亚基的同二聚体被证明是RNA/DNA结合蛋白，并作为转录辅因子发挥作用。NAC功能多样性是一种执行多种生物学功能的蛋白质（兼职蛋白）的典型例子。
