Differential proteolysis and evidence for a residue exchange in tissue plasminogen activator suggest possible association between two types of protein microheterogeneity.
The N-terminal part of native one-chain tissue plasminogen activator from melanoma cells is not homogeneous. The protein chain starts at two different positions, in all probability representing a processing difference in the N-terminus. Both 'long' L-chains and 3-residue shorter S-chains are present in the preparations. In addition, results compatible with a positional Ser/Gly microheterogeneity were obtained at a single position (position L-4 which is equal to S-1). The N-terminal tripeptide difference seems to be coupled to the possible microheterogeneity: L-chains contain Ser in this position, while S-chains appear to contain predominantly Gly.
D000595:Amino Acid Sequence; D002460:Cell Line; D003488:Cyanogen Bromide; D005341:Fibrinolysin; D006801:Humans; D008545:Melanoma / Q000032:analysis*; D010960:Plasminogen Activators
D010960:Plasminogen Activators; D005341:Fibrinolysin; D003488:Cyanogen Bromide