FIG. 1. Diagram of bovine proentero

FIG. 1. Diagram of bovine proenteropeptidase constructs. The scheme at the top indicates the domain structure of full-length bovine enteropeptidase predicted from the cDNA sequence (5). HL-BEK represents a secreted recombinant form in which the signal anchor (SA) and alternatively spliced (AE) domains were replaced by the prothrombin signal peptide and a His6 tag. L-BEK represents a form in which all but the extreme carboxyl terminus of the heavy chain was replaced by the signal peptide and a His6 tag. Other repeated motifs are labeled: LDLR, low density lipoprotein receptor-like domain; C1r/s, complement component C1r- or C1s-like domain; MAM, a domain named for similarity to meprin, X. laevis A5 protein, and protein tyrosine phosphatase Mu; MSCR, macrophage scavenger receptor-like domain. The arrows indicate the proteolytic activation cleavage site between the heavy and light chains of two-chain enteropeptidase. The disulfide bond linking the heavy and light chains (–SS–) and the active-site residues His (H), Asp (D), and Ser (S) are indicated (5).