title: 240-kDa proteasome inhibitor (CF-2) is identical to delta-aminolevulinic acid dehydratase.
abstract: The 240-kDa proteasome inhibitor has been reported to be an ATP-stabilized component (CF-2) of the 26 S proteasome complex. We now report that this inhibitory factor is indistinguishable from delta-aminolevulinic acid dehydratase (ALAD), the second enzyme in the pathway of heme synthesis, based upon the following observations: 1) common sequence of the first 14 N-terminal amino acids; 2) identical migration on native and SDS-polyacrylamide gel electrophoresis; 3) identical isoelectric points of pH 7.1; 4) cross-reactivity of specific polyclonal antibodies; 5) similar dehydratase and proteasome inhibitor specific activities in both proteins; and 6) the presence of both activities in recombinant ALAD. The dual role of this protein as CF-2 in the ATP/ubiquitin-dependent pathway and in heme synthesis may be an example of "gene sharing" and explains the unexpected abundance of ALAD noted in earlier studies.
authors.affiliation: Department of Cell Biology and Anatomy, New York Medical College, Valhalla 10595.
authors.forename: G G
authors.initials: GG
authors.lastname: Guo
authors.forename: M
authors.initials: M
authors.lastname: Gu
authors.forename: J D
authors.initials: JD
authors.lastname: Etlinger
mesh_terms: D000906:Antibodies / Q000276:immunology; D015153:Blotting, Western; D003429:Cross Reactions; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006418:Heme / Q000096:biosynthesis; D006801:Humans; D009097:Multienzyme Complexes / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism*; D000623:Porphobilinogen Synthase / Q000276:immunology / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex
chemical_list: D000906:Antibodies; D009097:Multienzyme Complexes; D006418:Heme; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; D000623:Porphobilinogen Synthase