A comparative study of the 50S ribosomal subunit and several 50S subparticles in EF-T-and EF-G-dependent activities.

A series of ribosomal subparticles derived from the 50S subunit has been studied and compared in EF-T- and EF-G-dependent reactions. Three different 50S cores were prepared by CsC1 isophycnic centrifugation and one by NH(4)Cl-ethanol extractionm the 50S CsCl core a had lost proteins L1, L7, L8, L10, L12, L16, L25, L33, and some L6 and L11. The 50S CsCl core b additionally lacked protein L6, and 50S CsCl core c also lacked protein L5, L15, L18, L27, L28, L30, and most of L9, L14, L19, and L21. The 50S NH(4)Cl-ethanol core had lost up to 90 percent of proteins L7, L12 and 30-60 percent of proteins L8, L10, and L29. The 50S CsCl core a had much reduced activity in EF-G and none in EF-T GTPase reactions while 50S CsCl cores b and c were inactive. Addition of proteins L7, L12 restored the activity for both the EF-T- and EF-G-dependent GTPase with all of the three 50S CsCl cores, increasing stepwise from core c to core a; The 50S NH(4)Cl-ethanol core was partially active in the EF-G GTPase over the 2-30 mM MG-2+ range tested, while EF-T only showed some activity inthe upper portion of this range...