An electrophoretically silent polymorphism for the beta chains of rabbit hemoglobin and associated polyribosome...

The beta chain of rabbit (Oryctolagus caniculus) hemoglobin has previously been reported to contain a single residue of isoleucine at beta(112). We have detected other rabbits with either zero isoleucyl residues or half a residue per beta chain. This character is polymorphic and inherited as a simple mendelian autosomal codominant.-Normally the modal number of ribosomes per polyribosome is 4 to 6 in reticulocyte lysates; but incubation of rabbit reticulocytes prior to lysis with L-o-methylthreonine (OMT), an isostere of isoleucine, leads to a bimodal distribution in lysates with 2-3 and 8-12 ribosomes as modes. This alteration has been attributed to ribosomal traffic jams caused by starvation for ile-tRNA at mRNA codons corresponding to the locations of isoleucyl residues at positions alpha(10), alpha(17), alpha(55) and beta(112). We have confirmed this interpretation by incubating OMT with reticulocytes from rabbits with integral, half integral and nil values for isoleucyl residues per beta chain to show that formation of the larger clusters of polyribosomes requires that beta(112) = ile.