PMID- 2822082
OWN - NLM
STAT- MEDLINE
DCOM- 19871207
LR  - 20190613
IS  - 0006-2960 (Print)
IS  - 0006-2960 (Linking)
VI  - 26
IP  - 14
DP  - 1987 Jul 14
TI  - Purification and characterization of protein carboxyl methyltransferase from 
      Torpedo ocellata electric organ.
PG  - 4200-6
AB  - Posttranslational modification of proteins by the enzyme protein carboxyl 
      methyltransferase (PCM) has been associated with a variety of cellular functions. 
      A prerequisite for the understanding of cellular mechanisms associated with PCM 
      is the characterization of purified PCMs from different tissues. We describe here 
      the purification and characterization of PCM from the electric organ of Torpedo 
      ocellata. The enzyme was purified to homogeneity by ion-exchange chromatography 
      and ammonium sulfate precipitation, followed by chromatography on Sephadex G-100 
      and hydroxylapatite columns. When visualized by silver staining, the 
      700-fold-purified PCM exhibited a single band on sodium dodecyl 
      sulfate-polyacrylamide gels, corresponding to a polypeptide of Mr 29,000. The 
      molecular weight of the nondenatured enzyme (as determined by rechromatography on 
      Sephadex G-100 column) was also 29,000, suggesting that the enzyme is a monomer. 
      Two isoelectric forms of PCM (pI = 6.1 and pI = 6.4) were detected in the 
      purified enzyme preparation. The enzyme methylates various exogenous and 
      endogenous proteins, including the acetylcholine receptor. Of the four different 
      polypeptides of the acetylcholine receptor, the gamma and beta polypeptides were 
      selectively methylated by the purified PCM. Purified Torpedo PCM is highly 
      sensitive to sulfhydryl reagents. The competitive inhibitor of PCM 
      S-adenosyl-L-homocysteine (AdoHcy) protected the enzyme from inactivation by 
      sulfhydryl reagents, suggesting the existence of a cysteine residue at the active 
      site of the enzyme. The purified PCM has a low affinity toward DEAE-cellulose and 
      toward AdoHcy-agarose. This property, as well as the relatively high molecular 
      weight and the marked sensitivity to sulfhydryl reagents, distinguishes between 
      the electric organ PCM and analogous enzymes of mammalian tissues.
FAU - Haklai, R
AU  - Haklai R
AD  - Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv 
      University, Israel.
FAU - Kloog, Y
AU  - Kloog Y
LA  - eng
PT  - Journal Article
PL  - United States
TA  - Biochemistry
JT  - Biochemistry
JID - 0370623
RN  - 0 (Hydroxyapatites)
RN  - 91D9GV0Z28 (Durapatite)
RN  - EC 2.1.1.- (Protein Methyltransferases)
RN  - EC 2.1.1.- (Protein O-Methyltransferase)
SB  - IM
MH  - Animals
MH  - Chromatography/methods
MH  - Chromatography, DEAE-Cellulose/methods
MH  - Chromatography, Gel/methods
MH  - Durapatite
MH  - Electric Organ/*enzymology
MH  - Hydroxyapatites
MH  - Kinetics
MH  - Molecular Weight
MH  - Protein Methyltransferases/*isolation & purification
MH  - Protein O-Methyltransferase/*isolation & purification/metabolism
MH  - Torpedo
EDAT- 1987/07/14 00:00
MHDA- 1987/07/14 00:01
CRDT- 1987/07/14 00:00
PHST- 1987/07/14 00:00 [pubmed]
PHST- 1987/07/14 00:01 [medline]
PHST- 1987/07/14 00:00 [entrez]
AID - 10.1021/bi00388a004 [doi]
PST - ppublish
SO  - Biochemistry. 1987 Jul 14;26(14):4200-6. doi: 10.1021/bi00388a004.