Structure-function studies of the epidermal growth factor domains of human thrombomodulin.
Structure-function relationships in the 6 epidermal growth factor-like domains of human thrombomodulin (TME, residues 227-462) were studied by deletion mutagenesis. Purified and characterised proteins were used for kinetic studies. Deletion of EGF1, EGF2 and residues 310-332 in EGF3 had no effect on thrombin binding (Kd) or on kcat/KM for protein C activation by the thrombin-thrombomodulin complex. Deletion of the rest of EGF3 and the interdomain loop between EGF3 and EGF4 had no effect on Kd but decreased kcat/KM to 10% of TME. Deletion of residues 447-462 of EGF6 had no effect on kcat/KM but increased Kd for thrombin approximately 6-fold. Thus, the region 333-350 in EGF3-4 is critical for protein C activation by the thrombin-thrombomodulin complex and the region 447-462 in EGF6 is critical for thrombin binding.
Parkinson
J F
JF
Berlex Biosciences Inc., South San Francisco, CA 94080.
Nagashima
M
M
Kuhn
I
I
Leonard
J
J
Morser
J
J
D001483:Base Sequence; D004252:DNA Mutational Analysis; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000737:chemistry; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D011486:Protein C / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000737:chemistry* / Q000378:metabolism; D018179:Receptors, Thrombin; D011994:Recombinant Proteins; D013329:Structure-Activity Relationship; D013917:Thrombin / Q000378:metabolism
D009838:Oligodeoxyribonucleotides; D011486:Protein C; D011956:Receptors, Cell Surface; D018179:Receptors, Thrombin; D011994:Recombinant Proteins; D004815:Epidermal Growth Factor; D013917:Thrombin