Burkard G, Keller E B
Section of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, New York 14850.
Proc Natl Acad Sci U S A. 1974 Feb;71(2):389-93. doi: 10.1073/pnas.71.2.389.
Extracts of wheat chloroplasts contain a poly(A) polymerase which can polymerize AMP residues from ATP onto an RNA primer. Whole extracts of wheat leaves also contain another poly(A) polymerase which is present in much larger amount and is probably derived from the nuclei. Both polymerases can utilize as primer poly(A), poly(C), transfer RNA, and ribosomal RNA, but only the chloroplast polymerase can utilize poly(U) and poly(G). Both enzymes have a specific requirement for ATP. Extracts of wheat chloroplasts contain, in addition to the poly(A) polymerase, a poly(G) polymerase which can polymerize GMP residues from GTP onto primers such as poly(G), poly(A), or ribosomal RNA. The poly(G) polymerase cannot utilize ATP but can slowly polymerize CMP from CTP. When the two chloroplast polymerases are present together in an in vitro incubation with ATP plus GTP and poly(A), the polymerization product is a mixed poly(A,G) tract.
小麦叶绿体提取物含有一种聚腺苷酸聚合酶，它能将ATP中的AMP残基聚合到RNA引物上。小麦叶片的全提取物还含有另一种聚腺苷酸聚合酶，其含量要多得多，可能来源于细胞核。两种聚合酶都可以将聚腺苷酸、聚胞苷酸、转移RNA和核糖体RNA用作引物，但只有叶绿体聚合酶可以利用聚尿苷酸和聚鸟苷酸。两种酶都对ATP有特定需求。除了聚腺苷酸聚合酶外，小麦叶绿体提取物还含有一种聚鸟苷酸聚合酶，它能将GTP中的GMP残基聚合到诸如聚鸟苷酸、聚腺苷酸或核糖体RNA等引物上。聚鸟苷酸聚合酶不能利用ATP，但能缓慢地将CTP中的CMP聚合。当两种叶绿体聚合酶与ATP加GTP以及聚腺苷酸一起在体外孵育时，聚合产物是混合的聚（A，G）序列。
