Identification of probasin-related antigen as cystathionine gamma-lyase by molecular cloning.
We reported previously that a monoclonal antibody against probasin (rat prostatic secretory protein) recognizes a 40-kDa protein localized in rat liver and kidney. The protein (probasin-related antigen, PRB-RA) may participate in a specific differentiated function of these tissues. To clarify the molecular nature of PRB-RA, a series of cDNA clones coding for the protein were isolated from a rat liver expression library using an affinity-purified polyclonal antibody. The amino acid sequence deduced from the determined cDNA sequence included sequences identical with those of proteolytic fragments of PRB-RA, which covered about 70% of the deduced sequence. Northern blot hybridization of poly(A)+ RNA isolated from rat tissues showed the presence of predominant and minor mRNA species of about 2.0 and 4.3 kilobases, respectively, in the liver and kidney. A sequence homology search revealed that PRB-RA is almost completely identical to rat cystathionine gamma-lyase (cystathionase) and that it does not show overall homology with probasin. Three candidates for an epitope common to probasin and PRB-RA were found on close examination of the amino acid sequences of the two proteins. A synthetic peptide, TYFRRI, corresponding to one of the candidates, neutralized the reactivity of the anti-probasin monoclonal antibody to both probasin and PRB-RA on Western blot analysis. These results show that PRB-RA/cystathionase is neither structurally nor functionally related to probasin except for a common epitope and that cystathionase, a cystein-producing enzyme, is localized in urinary tubular epithelial cells in a highly restricted region of the kidney in addition to in liver parenchymal cells.
Nishi
N
N
Department of Endocrinology, Kagawa Medical School, Japan.
Tanabe
H
H
Oya
H
H
Urushihara
M
M
Miyanaka
H
H
Wada
F
F
D000595:Amino Acid Sequence; D000727:Androgen-Binding Protein / Q000737:chemistry* / Q000276:immunology; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D003001:Cloning, Molecular; D003542:Cystathionine gamma-Lyase / Q000235:genetics* / Q000276:immunology; D015870:Gene Expression; D008297:Male; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D000727:Androgen-Binding Protein; D012333:RNA, Messenger; C027519:probasin; D003542:Cystathionine gamma-Lyase