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. 1975 Feb 25;250(4):1197-206.

Purification and characterization of homogeneous protein synthesis initiation factor M1 from rabbit reticulocytes

  • PMID: 1112800
Free article

Purification and characterization of homogeneous protein synthesis initiation factor M1 from rabbit reticulocytes

W C Merrick et al. J Biol Chem. .
Free article

Abstract

An eight-step procedure has been devised for the preparation of homogeneous rabbit reticulocyte IF-M1. Molecular weight determinations based on IF-M1 activity (gel filtration and sucrose density gradient sedimentation) and based on IF-M1 protein (low speed equilibrium sedimentation and sodium dodecyl sulfate gel electrophoresis) indicate that IF-M1 is active as a single polypeptide chain of 65,000 molecular weight. The amino acid composition of IF-M1 has been determined. There appears to be no unique features in the amino acid composition of IF-M1, except perhaps an elevated proline content (6.9 mol %). The catalytic properties of purified IF-M1 were similar to those previously reported by this laboratory for crude preparations of IF-M1. The sensitivity of IF-M1 activity to N-ethylmaleimide and heat (45 degrees) inactivation was tested in two model reactions requiring minimal complementary factors: (a) AUG-directed fMet-tRNAf binding to ribosomes; and (b) poly(U)-directed polyphenylalanine synthesis at 4 mM Mg2+ (IF-M2A, IF-M2B, EF-1, and EF-2 also required). IF-M1 activity proved to be sensitive to both N-ethylmaleimide and temperature (45 degrees). In addition, a contaminant of partially purified IF-M1 preparations has been found which is capable of fMet-tRNAf binding but is inactive in poly(U)-directed polyphenylalanine synthesis at low Mg2+ concentration.

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