Chemical cross-linking of MtM proteins visualised by SDS-PAGE.

Profiles of lanes 1–5 are as follows: 1, MtM; 2, MtM treated with 0.15 mM DSS; 3, MtM treated with 0.31 mM DSS; 4, MtM treated with 0.63 mM DSS and 5, MtM treated with 1.25 mM DSS. Box B shows the profile of MtM proteins (lane 1) which were cross-linked (lanes 2–3) by 0.15–0.31 mM DSS, as opposed to the proteins (box C, lanes 2–3) which were not cross-linked. Further increases in DSS concentration (lanes 4 and 5) led to a ‘non-specific’ cross-linking of proteins [36] in box C as well as other gel areas. Lane 2 in box A shows enhanced protein staining, most probably due to the accumulation of protein complexes formed by cross-linking. Corresponding area in lanes 3–5 gradually lost the staining intensity despite enhanced cross-linking. In this case, the complexes may have been too large to enter the gel.