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Translation of Synthetic and Endogenous Messenger Ribonucleic Acid In Vitro by Ribosomes and Polyribosomes from Clostridium pasteurianum

Department of Biochemistry, University of Kansas, Lawrence, Kansas 66044, and Department of Biochemistry, University of California, Berkeley, California 94720

ABSTRACT

Ribosomes and polyribosomes from Clostridium pasteurianum were isolated and their activities were compared with those of ribosomes from Escherichia coli in protein synthesis in vitro. C. pasteurianum ribosomes exhibited a high level of activity due to endogenous messenger ribonucleic acid (RNA). For translation of polyuridylic acid [poly(U)], C. pasteurianum ribosomes required a higher concentration of Mg²⁺ and a much higher level of poly(U) than did E. coli ribosomes. Phage f2 RNA added to the system with C. pasteurianum ribosomes gave no significant stimulation of protein synthesis in a homologous system or with E. coli initiation factors. The 30S and 50S subunits prepared from C. pasteurianum ribosomes reassociated less readily than subunits from E. coli. The ability of the C. pasteurianum subunits to reassociated was found to be dependent upon the presence of a reducing agent during preparation and during analysis of the reassociation products. In heterologous combinations, E. coli 30S subunits associated readily with C. pasteurianum 50S subunits to form 70S particles, but C. pasteurianum 30S subunits and E. coli 50S subunits did not associate. In poly(U) translation, E. coli 30S subunits were active in combination with 50S subunits from either E. coli or C. pasteurianum, but C. pasteurianum 30S subunits were not active in combination with either type of 50S subunits. Polyribosomes prepared from C. pasteurianum were very active in protein synthesis, and well-defined ribosomal aggregates as large as heptamers could be seen on sucrose gradients. An attempt was made to demonstrate synthesis in vitro of ferredoxin.