The ribosomal protein L7/L12 with the substitution of Cys(38) for the
Val(38) residue was obtained and studied to test the orientation of po
lypeptide chains in the N-terminal region of the dimer, The results sh
ow that the L7/L12 dimer has a parallel (head-to-head) orientation of
subunits and that its first 37 N-terminal residues are sufficient for
dimerization.