The polymerization of guanosine diphosphate by polynucletide phosphorylase.

Polynucleotide phosphorylase catalyzes the reversible polytion of nucleoside diphosphates (1). With enzyme prepns from Escherichia coli (2), Azotobacter agile (3), and Mius lysodeikticus (4, 5) a reaction has been observed with additions of adenosine, uridine, cytosine, or inosine diphosto form the corresponding homopolymer. However, the erization of guanosine diphosphate represents a special . Littauer and Kornberg (2) observed no polymerization tion upon incubating GDP with fractions from E. coli. In otide phosphorylase from A . agile, noted a very slow release of PI from ped far short of the equilibrium point . In contrast, when mixed with other leoside diphosphates, GDP is well utilized and polymers ly AGUC’ are formed (3). eriments described below show that GDP, when presis not polymerized even after many hours by enzyme rom A. agile or E. coli. However, polymerization of does take place in the presence of oligonucleotides such as and ApApU, and guanosine monophosphate units are the primer. No reaction occurs with GDP and oligoes, such as ApApUp, that do not contain an unsubstidroxyl group at carbon 3’ of the terminal nucleoside due. Highly purified fractions of A . agile polynucleotide phorylase, kindly supplied by Drs. Mii and Ochoa (6), catathe polymerization of ADP, UDP, CDP, and IDP only afa lag period. Thii lag can be overcome by ribonucleic acid ertain other polymers (6), as well as by oligoribonucleotides us types, including pApApA, ApApU and ApApUp (see g paper (7)). Accordingly, GDP differs from other nudiphosphates in that its polymerization requires the sence of oligonucleotides of the type that can be incorporated