PMID- 24124590
OWN - NLM
STAT- MEDLINE
DCOM- 20140522
LR  - 20211021
IS  - 1932-6203 (Electronic)
IS  - 1932-6203 (Linking)
VI  - 8
IP  - 10
DP  - 2013
TI  - Residues in human arsenic (+3 oxidation state) methyltransferase forming 
      potential hydrogen bond network around S-adenosylmethionine.
PG  - e76709
LID - 10.1371/journal.pone.0076709 [doi]
LID - e76709
AB  - Residues Tyr59, Gly78, Ser79, Met103, Gln107, Ile136 and Glu137 in human arsenic 
      (+3 oxidation state) methyltransferase (hAS3MT) were deduced to form a potential 
      hydrogen bond network around S-adenosylmethionine (SAM) from the sequence 
      alignment between Cyanidioschyzon merolae arsenite S-adenosylmethyltransferase 
      (CmArsM) and hAS3MT. Herein, seven mutants Y59A, G78A, S79A, M103A, Q107A, I136A 
      and E137A were obtained. Their catalytic activities and conformations were 
      characterized and models were built. Y59A and G78A were completely inactive. Only 
      7.0%, 10.6% and 13.8% inorganic arsenic (iAs) was transformed to monomethylated 
      arsenicals (MMA) when M103A, Q107A and I136A were used as the enzyme. The Vmax 
      (the maximal velocity of the reaction) values of M103A, Q107A, I136A and E137A 
      were decreased to 8%, 22%, 15% and 50% of that of WT-hAS3MT, respectively. The 
      KM(SAM) (the Michaelis constant for SAM) values of mutants M103A, I136A and E137A 
      were 15.7, 8.9 and 5.1 fold higher than that of WT-hAS3MT, respectively, 
      indicating that their affinities for SAM were weakened. The altered 
      microenvironment of SAM and the reduced capacity of binding arsenic deduced from 
      KM(As) (the Michaelis constant for iAs) value probably synergetically reduced the 
      catalytic activity of Q107A. The catalytic activity of S79A was higher than that 
      of WT despite of the higher KM(SAM) , suggesting that Ser79 did not impact the 
      catalytic activity of hAS3MT. In short, residues Tyr59 and Gly78 significantly 
      influenced the catalytic activity of hAS3MT as well as Met103, Ile136 and Glu137 
      because they were closely associated with SAM-binding, while residue Gln107 did 
      not affect SAM-binding regardless of affecting the catalytic activity of hAS3MT. 
      Modeling and our experimental results suggest that the adenine ring of SAM is 
      sandwiched between Ile136 and Met103, the amide group of SAM is hydrogen bonded 
      to Gly78 in hAS3MT and SAM is bonded to Tyr59 with van der Waals, cation-pi and 
      hydrogen bonding contacts.
FAU - Li, Xiangli
AU  - Li X
AD  - State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical 
      Engineering, Nanjing University, Nanjing, PR China.
FAU - Cao, Jing
AU  - Cao J
FAU - Wang, Shuping
AU  - Wang S
FAU - Geng, Zhirong
AU  - Geng Z
FAU - Song, Xiaoli
AU  - Song X
FAU - Hu, Xin
AU  - Hu X
FAU - Wang, Zhilin
AU  - Wang Z
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20131004
PL  - United States
TA  - PLoS One
JT  - PloS one
JID - 101285081
RN  - 0 (Amino Acids)
RN  - 0 (Recombinant Proteins)
RN  - 7LP2MPO46S (S-Adenosylmethionine)
RN  - EC 2.1.1.- (Methyltransferases)
RN  - EC 2.1.1.137 (AS3MT protein, human)
RN  - N712M78A8G (Arsenic)
SB  - IM
MH  - Amino Acids
MH  - Arsenic/chemistry/metabolism
MH  - Binding Sites
MH  - Catalysis
MH  - Gene Expression
MH  - Humans
MH  - Hydrogen Bonding
MH  - Kinetics
MH  - Methylation
MH  - Methyltransferases/*chemistry/genetics/metabolism
MH  - Models, Molecular
MH  - Mutation
MH  - Protein Binding
MH  - Protein Conformation
MH  - Recombinant Proteins/chemistry/genetics/isolation & purification/metabolism
MH  - S-Adenosylmethionine/*chemistry/metabolism
MH  - Substrate Specificity
PMC - PMC3790734
COIS- Competing Interests: The authors have declared that no competing interests exist.
EDAT- 2013/10/15 06:00
MHDA- 2014/05/23 06:00
PMCR- 2013/10/04
CRDT- 2013/10/15 06:00
PHST- 2013/06/07 00:00 [received]
PHST- 2013/08/27 00:00 [accepted]
PHST- 2013/10/15 06:00 [entrez]
PHST- 2013/10/15 06:00 [pubmed]
PHST- 2014/05/23 06:00 [medline]
PHST- 2013/10/04 00:00 [pmc-release]
AID - PONE-D-13-23687 [pii]
AID - 10.1371/journal.pone.0076709 [doi]
PST - epublish
SO  - PLoS One. 2013 Oct 4;8(10):e76709. doi: 10.1371/journal.pone.0076709. eCollection 
      2013.