PMID- 20543879
OWN - NLM
STAT- MEDLINE
DCOM- 20100901
LR  - 20211020
IS  - 1932-6203 (Electronic)
IS  - 1932-6203 (Linking)
VI  - 5
IP  - 6
DP  - 2010 Jun 3
TI  - Structure-function relations in oxaloacetate decarboxylase complex. Fluorescence 
      and infrared approaches to monitor oxomalonate and Na(+) binding effect.
PG  - e10935
LID - 10.1371/journal.pone.0010935 [doi]
LID - e10935
AB  - BACKGROUND: Oxaloacetate decarboxylase (OAD) is a member of the Na(+) transport 
      decarboxylase enzyme family found exclusively in anaerobic bacteria. OAD of 
      Vibrio cholerae catalyses a key step in citrate fermentation, converting the 
      chemical energy of the decarboxylation reaction into an electrochemical gradient 
      of Na(+) ions across the membrane, which drives endergonic membrane reactions 
      such as ATP synthesis, transport and motility. OAD is a membrane-bound enzyme 
      composed of alpha, beta and gamma subunits. The alpha subunit contains the 
      carboxyltransferase catalytic site. METHODOLOGY/PRINCIPAL FINDINGS: In this 
      report, spectroscopic techniques were used to probe oxomalonate (a competitive 
      inhibitor of OAD with respect to oxaloacetate) and Na(+) effects on the enzyme 
      tryptophan environment and on the secondary structure of the OAD complex, as well 
      as the importance of each subunit in the catalytic mechanism. An intrinsic 
      fluorescence approach, Red Edge Excitation Shift (REES), indicated that solvent 
      molecule mobility in the vicinity of OAD tryptophans was more restricted in the 
      presence of oxomalonate. It also demonstrated that, although the structure of OAD 
      is sensitive to the presence of NaCl, oxomalonate was able to bind to the enzyme 
      even in the absence of Na(+). REES changes due to oxomalonate binding were also 
      observed with the alphagamma and alpha subunits. Infrared spectra showed that 
      OAD, alphagamma and alpha subunits have a main component band centered between 
      1655 and 1650 cm(-1) characteristic of a high content of alpha helix structures. 
      Addition of oxomalonate induced a shift of the amide-I band of OAD toward higher 
      wavenumbers, interpreted as a slight decrease of beta sheet structures and a 
      concomitant increase of alpha helix structures. Oxomalonate binding to alphagamma 
      and alpha subunits also provoked secondary structure variations, but these 
      effects were negligible compared to OAD complex. CONCLUSION: Oxomalonate binding 
      affects the tryptophan environment of the carboxyltransferase subunit, whereas 
      Na(+) alters the tryptophan environment of the beta subunit, consistent with the 
      function of these subunits within the enzyme complex. Formation of a complex 
      between OAD and its substrates elicits structural changes in the alpha-helical as 
      well as beta-strand secondary structure elements.
FAU - Granjon, Thierry
AU  - Granjon T
AD  - Institute of Microbiology, Eidgenossische Technische Hochschule, Zurich, 
      Switzerland. thierry.granjon@univ-lyon1.fr
FAU - Maniti, Ofelia
AU  - Maniti O
FAU - Auchli, Yolanda
AU  - Auchli Y
FAU - Dahinden, Pius
AU  - Dahinden P
FAU - Buchet, Rene
AU  - Buchet R
FAU - Marcillat, Olivier
AU  - Marcillat O
FAU - Dimroth, Peter
AU  - Dimroth P
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20100603
PL  - United States
TA  - PLoS One
JT  - PloS one
JID - 101285081
RN  - 0 (Malonates)
RN  - 9NEZ333N27 (Sodium)
RN  - EC 4.1.1.- (Carboxy-Lyases)
RN  - EC 4.1.1.112 (oxaloacetate decarboxylase)
SB  - IM
MH  - Carboxy-Lyases/chemistry/*metabolism
MH  - Catalysis
MH  - Electrochemistry
MH  - Malonates/*metabolism
MH  - Models, Molecular
MH  - Protein Binding
MH  - Protein Structure, Secondary
MH  - Sodium/*metabolism
MH  - Spectrometry, Fluorescence/*methods
MH  - Spectrophotometry, Infrared/*methods
MH  - Structure-Activity Relationship
PMC - PMC2881705
COIS- Competing Interests: The authors have declared that no competing interests exist.
EDAT- 2010/06/15 06:00
MHDA- 2010/09/02 06:00
PMCR- 2010/06/03
CRDT- 2010/06/15 06:00
PHST- 2009/12/30 00:00 [received]
PHST- 2010/05/08 00:00 [accepted]
PHST- 2010/06/15 06:00 [entrez]
PHST- 2010/06/15 06:00 [pubmed]
PHST- 2010/09/02 06:00 [medline]
PHST- 2010/06/03 00:00 [pmc-release]
AID - 09-PONE-RA-15214R2 [pii]
AID - 10.1371/journal.pone.0010935 [doi]
PST - epublish
SO  - PLoS One. 2010 Jun 3;5(6):e10935. doi: 10.1371/journal.pone.0010935.