Out of expected protein size in SDS-PAGE - (Nov/13/2009 )

It is interesting to find same problem to mine.
I've had hard time in Western blot of some protein in human heart homogenates.
Western blot with recombinant protein-coding adenovirus infected cells (rat neonatal cardiomyocytes) showed predicted size (98kDa), but I've never got signal with human heart sample in that size. Instead, signal appeared as 250 kDa.

The other discussion in this forum said SDS binding in certain protein can be a cause of this kind of size-shift.