ECL SDS-PAGE detection of covalently bound heme in CtrHbs. (a) Ferric samples
were reducedwith 2mMDT for ~30min then re-oxidizedwith air before being subjected
to electrophoresis. The image was obtained with a 30-s exposure. The heme of WT CtrHb
and the T111H and L75H variants (lane 1-3) migrates at the dye front.WTGlbN-A (lane 4)
is included as a positive control for covalent linkage. (b) Ferric WT and variant CtrHbs
were first saturatedwith cyanide and then reduced for ~30min. The figure shows images
of film that was exposed for either 30 s or 7 min. The heme fromWT CtrHb (lane 1) migrates
with the dye front. The T111H CtrHb lane (lane 2) shows incomplete heme attachment.
The longer exposure time was necessary to observe the faint crosslinked T111H
CtrHb band. The L75H CtrHb lane (lane 3) shows complete crosslinking as in the GlbN-A
control (lane 4).