title: Biosynthesis of properdin.
abstract: Properdin (P) is synthesized by the human promyelocytic cell line, HL-60, after differentiation with DMSO. The secreted P was physiochemically indistinguishable from purified plasma P. It was polymerized and able to bind to C3IBb-Sepharose but not to C3i-Sepharose. No extracellular precursor was present. The intracellular form, detected between 1 and 4 h after labeling, was similar but had a slightly lower Mr. It also bound reversibly to C3iBb-Sepharose, and polymers could be demonstrated by cross-linking. Pulse-chase experiments suggested the existence of an earlier, but undetectable, intracellular precursor(s). This form could not be immunoprecipitated even when harsh solubilization conditions and/or antibodies against reduced and denatured P were utilized. Studies with endoglycosidases F and H and tunicamycin indicated that the detectable intracellular precursor contains high mannose N-linked carbohydrate that is processed to the complex form before secretion. The sugars are not required for polymerization, secretion, or functional activity, or responsible for the electrophoretic heterogeneity. Polymerization of P is therefore an early intracellular event, perhaps carefully controlled to prevent anomalous aggregation.
authors.affiliation: Howard Hughes Medical Institute Laboratories, St. Louis, MO 63110.
authors.forename: T C
authors.initials: TC
authors.lastname: Farries
authors.forename: J P
authors.initials: JP
authors.lastname: Atkinson
mesh_terms: D002236:Carbohydrate Conformation / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D003593:Cytoplasm / Q000187:drug effects; D004121:Dimethyl Sulfoxide; D006031:Glycosylation; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000378:metabolism*; D011414:Properdin / Q000096:biosynthesis* / Q000302:isolation & purification / Q000502:physiology; D011498:Protein Precursors / Q000096:biosynthesis / Q000302:isolation & purification / Q000502:physiology; D013329:Structure-Activity Relationship
chemical_list: D011498:Protein Precursors; D011414:Properdin; D004121:Dimethyl Sulfoxide