Cysteine carboxyl O-methylation of human placental 23 kDa protein.
- Author:
Kyeong Man HONG
1
;
Yong Bock CHOI
;
Jung Hee HONG
;
Hyun Shin CHANG
;
Kang Il RHEE
;
Hyun PARK
;
Moon Kee PAIK
Author Information
1. Department of Biochemistry, Wonkwang University School of Medicine, Chulla-bukdo, Korea.
- Publication Type:Original Article ; Research Support, Non-U.S. Gov't
- Keywords:
cysteine carboxyl O-methylation;
human placenta
- MeSH:
Cysteine/metabolism*;
Female;
GTP-Binding Proteins/metabolism*;
Guanine Nucleotides/pharmacology;
Human;
Methylation;
Placenta/metabolism*;
Placenta/enzymology;
Pregnancy;
Pregnancy Proteins/metabolism*;
Protein Methyltransferases/metabolism*
- From:Experimental & Molecular Medicine
1999;31(1):30-35
- CountryRepublic of Korea
- Language:English
-
Abstract:
C-Terminal carboxyl methylation of a human placental 23 kDa protein catalyzed by membrane-associated methyltransferase has been investigated. The 23 kDa protein substrate methylated was partially purified by DEAE-Sephacel, hydroxyapatite and Sephadex G-100 gel filtration chromatographies. The substrate protein was eluted on Sephadex G-100 gel filtration chromatography as a protein of about 29 kDa. In the absence of Mg2+, the methylation was stimulated by guanine nucleotides (GTP, GDP and GTPgammaS), but in the presence of Mg2+, only GTPgammaS stimulated the methylation which was similar to the effect on the G25K/rhoGDI complex. AFC, an inhibitor of C-terminal carboxyl methylation, inhibited the methylation of human placental 23 kDa protein. These results suggests that the substrate is a small G protein different from the G25K and is methylated on C-terminal isoprenylated cysteine residue. This was also confirmed by vapor phase analysis. The methylated substrate protein was redistributed to membrane after in vitro methylation, suggesting that the methylation of this protein is important for the redistribution of the 23 kDa small G protein for its putative role in intracellular signaling.
