FIG 4.

R36D K38E mutant RACK1 does not bind ribosomes efficiently. (A) Ribosome profiles coupled with Western blots show the distribution of RACK1-HaloTag in the profile fractions. rpS6 and eIF6 were used as markers of the 40S and 60S ribosomal subunits. Note the absence of mutant RACK1 from polysomes. (B) Western blotting was performed to assess the abilities of HaloTag-labeled wild-type and mutant RACK1 to copurify with 40S ribosomal proteins under conditions of mRNA degradation. (C) The ability of PKCβII to copurify with wild-type and mutant RACK1-HaloTag, independently of RACK1 binding to ribosomes, is shown by Western blotting on eluted samples. PMA, phorbol myristate acetate.