Fig. 5. Cross-linking of the GalR protein. Wild-type (lanes 1–3) and R282L mutant (lanes 4–6) proteins were cross-linked using DMS in the presence of 250 mM (lanes 2 and 5) or 500 mM (lanes 3 and 6) NaCl. In lanes 1 and 4, no DMS was added. Reaction products were separated by SDS–PAGE on a 4–12% gel. The positions of monomers (I), dimers (II), trimers (III) and tetramers (IV) of GalR are marked. Mark 12™ Standard (M; Invitrogen) was used to estimate the molecular weight of the products.