title: Defining the boundaries of the testis angiotensin I-converting enzyme ectodomain.
abstract: Numerous cytokines, receptors, and ectoenzymes, including angiotensin I-converting enzyme (ACE), are shed from the cell surface by limited proteolysis at the juxtamembrane stalk region. The membrane-proximal C domain of ACE has been implicated in sheddase-substrate recognition. We mapped the functional boundaries of the testis ACE ectodomain (identical to the C domain of somatic ACE) by progressive deletions from the N- and C-termini and analysing the effects on catalytic activity, stability, and shedding in transfected cells. We found that deletions extending beyond Leu37 at the N-terminus and Trp616 at the C-terminus abolished catalytic activity and shedding, either by disturbing the ectodomain conformation or by inhibiting maturation and surface expression. Based on these data and on sequence alignments, we propose that the boundaries of the ACE ectodomain are Asp40 at the N-terminus and Gly615 at the C-terminus.
authors.affiliation: Division of Medical Biochemistry, University of Cape Town Medical School, Observatory 7925, Cape Town, South Africa.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Chubb
authors.forename: Sylva L U
authors.initials: SL
authors.lastname: Schwager
authors.forename: Zenda L
authors.initials: ZL
authors.lastname: Woodman
authors.forename: Mario R W
authors.initials: MR
authors.lastname: Ehlers
authors.forename: Edward D
authors.initials: ED
authors.lastname: Sturrock
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D016466:CHO Cells; D002384:Catalysis; D006224:Cricetinae; D017353:Gene Deletion; D005998:Glycine / Q000737:chemistry; D006801:Humans; D007700:Kinetics; D008297:Male; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D009154:Mutation; D007703:Peptidyl-Dipeptidase A / Q000737:chemistry*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013737:Testis / Q000378:metabolism*; D014162:Transfection
chemical_list: D007703:Peptidyl-Dipeptidase A; D005998:Glycine