PMID- 19167370
OWN - NLM
STAT- MEDLINE
DCOM- 20090506
LR  - 20131121
IS  - 1872-7786 (Electronic)
IS  - 0009-2797 (Linking)
VI  - 179
IP  - 2-3
DP  - 2009 May 15
TI  - Structure-function roles of four cysteine residues in the human arsenic (+3 
      oxidation state) methyltransferase (hAS3MT) by site-directed mutagenesis.
PG  - 321-8
LID - 10.1016/j.cbi.2008.12.018 [doi]
AB  - Cysteine (Cys) residues are often crucial to the function and structure of 
      proteins. Cys157 and Cys207 in recombinant mouse arsenic (+3 oxidation state) 
      methyltransferase (AS3MT) are shown to be related to enzyme activity and 
      considered to be the catalytic sites. The roles of some conserved Cys residues in 
      the N-terminal region of the rat AS3MT also have been examined. However, little 
      is known about the roles of the Cys residues in the middle region. The metabolism 
      of inorganic arsenic in human is different from rat and mouse in some aspects 
      though the AS3MT has a high degree of similarity in these species. In order to 
      determine whether the Cys156 and Cys206 (corresponding to the catalytic sites, 
      Cys157 and Cys207 in the mouse AS3MT) in the hAS3MT act as the catalytic sites 
      and to study the roles of the Cys residues (Cys226 and Cys250) near the catalytic 
      center in the middle region, we designed and prepared four mutants (C156S, C206S, 
      C226S, and C250S) in which one Cys residue replaced by serine by PCR-based 
      site-directed mutagenesis. The native form and cysteine/serine mutants were 
      assayed for enzyme activity, free thiols, and the secondary structures by 
      circular dichroism and Fourier transform infrared. Our data show that, besides 
      C156S and C206S, C250S is another potential important site. C226S seems to have 
      the same action as the wild-type hAS3MT with the consistent K(M) and V(max) 
      values. Meanwhile, selenium can also inhibit the methylation of inorganic arsenic 
      by C226S. All the mutants except C226S are calculated to have dramatic changes in 
      the secondary structures. Cys250 might form an intramolecular disulfide bond with 
      another Cys residue. These findings demonstrate that Cys residues at positions 
      156, 206, and 250 play important roles in the enzymatic function and structure of 
      the hAS3MT.
FAU - Song, Xiaoli
AU  - Song X
AD  - State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical 
      Engineering, Nanjing University, Hankou Road 22, Nanjing 210093, PR China.
FAU - Geng, Zhirong
AU  - Geng Z
FAU - Zhu, Jingshu
AU  - Zhu J
FAU - Li, Chengying
AU  - Li C
FAU - Hu, Xin
AU  - Hu X
FAU - Bian, Ningsheng
AU  - Bian N
FAU - Zhang, Xinrong
AU  - Zhang X
FAU - Wang, Zhilin
AU  - Wang Z
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20090110
PL  - Ireland
TA  - Chem Biol Interact
JT  - Chemico-biological interactions
JID - 0227276
RN  - 452VLY9402 (Serine)
RN  - EC 2.1.1.- (Methyltransferases)
RN  - EC 2.1.1.137 (AS3MT protein, human)
RN  - H6241UJ22B (Selenium)
RN  - K848JZ4886 (Cysteine)
RN  - N712M78A8G (Arsenic)
SB  - IM
MH  - Arsenic/antagonists & inhibitors/metabolism/toxicity
MH  - Circular Dichroism
MH  - Cysteine/*genetics/*metabolism
MH  - Dose-Response Relationship, Drug
MH  - Humans
MH  - Kinetics
MH  - Methylation
MH  - Methyltransferases/chemistry/*genetics/*metabolism
MH  - *Mutagenesis, Site-Directed
MH  - Protein Structure, Secondary
MH  - Selenium/pharmacology
MH  - Serine/genetics/metabolism
MH  - Spectroscopy, Fourier Transform Infrared
MH  - Structure-Activity Relationship
EDAT- 2009/01/27 09:00
MHDA- 2009/05/07 09:00
CRDT- 2009/01/27 09:00
PHST- 2008/10/12 00:00 [received]
PHST- 2008/12/13 00:00 [revised]
PHST- 2008/12/29 00:00 [accepted]
PHST- 2009/01/27 09:00 [entrez]
PHST- 2009/01/27 09:00 [pubmed]
PHST- 2009/05/07 09:00 [medline]
AID - S0009-2797(09)00002-7 [pii]
AID - 10.1016/j.cbi.2008.12.018 [doi]
PST - ppublish
SO  - Chem Biol Interact. 2009 May 15;179(2-3):321-8. doi: 10.1016/j.cbi.2008.12.018. 
      Epub 2009 Jan 10.