PMID- 10514445
OWN - NLM
STAT- MEDLINE
DCOM- 19991119
LR  - 20191210
IS  - 0021-9258 (Print)
IS  - 0021-9258 (Linking)
VI  - 274
IP  - 42
DP  - 1999 Oct 15
TI  - Expression and functional interaction of the catalytic and regulatory subunits of
      human methionine adenosyltransferase in mammalian cells.
PG  - 29720-5
AB  - Methionine adenosyltransferase (MAT) catalyzes the synthesis of
      S-adenosylmethionine (AdoMet). The mammalian MAT II isozyme consists of catalytic
      alpha(2) and regulatory beta subunits. The aim of this study was to investigate
      the interaction and kinetic behavior of the human MAT II subunit proteins in
      mammalian cells. COS-1 cells were transiently transfected with pTargeT vector
      harboring full-length cDNA that encodes for the MAT II alpha(2) or beta subunits.
      Expression of the His-tagged recombinant alpha(2) (ralpha(2)) subunit in COS-1
      cells markedly increased MAT II activity and resulted in a shift in the K(m) for 
      L-methionine (L-Met) from 15 microM (endogenous MAT II) to 75 microM (ralpha(2)),
      and with the apparent existence of two kinetic forms of MAT in the transfected
      COS-1 cell extracts. By contrast, expression of the recombinant beta (rbeta)
      subunit had no effect on the K(m) for L-Met of the endogenous MAT II, while it
      did cause an increase in both the V(max) and the specific activity of endogenous 
      MAT. Co-expression of both ralpha(2) and rbeta subunits resulted in a significant
      increase of MAT specific activity with the appearance of a single kinetic form of
      MAT (K(m) = 20 microM). The recombinant MAT II alpha(2) and rbeta subunit
      associated spontaneously either in cell-free system or in COS-1 cells
      co-expressing both subunits. Analysis of nickel-agarose-purified His-tagged
      ralpha(2) subunit from COS-1 cell extracts showed that the beta subunit
      co-purified with the alpha(2) subunit. Furthermore, the alpha(2) and beta
      subunits co-migrated in native polyacrylamide gels. Together, the data provide
      evidence for alpha(2) and beta MAT subunit association. In addition, the beta
      subunit regulated MAT II activity by reducing its K(m) for L-Met and by rendering
      the enzyme more susceptible to feedback inhibition by AdoMet. We believe that the
      previously described differential expression of MAT II beta subunit may be an
      important mechanism by which MAT activity can be modulated to provide different
      levels of AdoMet that may be required at different stages of cell growth and
      differentiation.
FAU - Halim, A B
AU  - Halim AB
AD  - Department of Surgery, University of Tennessee, Memphis, Tennessee 38104, USA.
FAU - LeGros, L
AU  - LeGros L
FAU - Geller, A
AU  - Geller A
FAU - Kotb, M
AU  - Kotb M
LA  - eng
GR  - GM-54892-08/GM/NIGMS NIH HHS/United States
PT  - Journal Article
PT  - Research Support, U.S. Gov't, Non-P.H.S.
PT  - Research Support, U.S. Gov't, P.H.S.
PL  - United States
TA  - J Biol Chem
JT  - The Journal of biological chemistry
JID - 2985121R
RN  - 0 (Recombinant Proteins)
RN  - EC 2.5.1.6 (Methionine Adenosyltransferase)
SB  - IM
MH  - Animals
MH  - COS Cells
MH  - Catalytic Domain
MH  - Chlorocebus aethiops
MH  - Humans
MH  - Kinetics
MH  - Methionine Adenosyltransferase/*metabolism
MH  - Recombinant Proteins/metabolism
EDAT- 1999/10/09 00:00
MHDA- 1999/10/09 00:01
CRDT- 1999/10/09 00:00
PHST- 1999/10/09 00:00 [pubmed]
PHST- 1999/10/09 00:01 [medline]
PHST- 1999/10/09 00:00 [entrez]
AID - 10.1074/jbc.274.42.29720 [doi]
PST - ppublish
SO  - J Biol Chem. 1999 Oct 15;274(42):29720-5. doi: 10.1074/jbc.274.42.29720.