PMID- 21255385
OWN - NLM
STAT- MEDLINE
DCOM- 20110426
LR  - 20211020
IS  - 1741-7007 (Electronic)
IS  - 1741-7007 (Linking)
VI  - 9
DP  - 2011 Jan 21
TI  - Shaping mechanisms of metal specificity in a family of metazoan metallothioneins: 
      evolutionary differentiation of mollusc metallothioneins.
PG  - 4
LID - 10.1186/1741-7007-9-4 [doi]
AB  - BACKGROUND: The degree of metal binding specificity in metalloproteins such as 
      metallothioneins (MTs) can be crucial for their functional accuracy. Unlike most 
      other animal species, pulmonate molluscs possess homometallic MT isoforms loaded 
      with Cu(+) or Cd(2+). They have, so far, been obtained as native metal-MT 
      complexes from snail tissues, where they are involved in the metabolism of the 
      metal ion species bound to the respective isoform. However, it has not as yet 
      been discerned if their specific metal occupation is the result of a rigid 
      control of metal availability, or isoform expression programming in the hosting 
      tissues or of structural differences of the respective peptides determining the 
      coordinative options for the different metal ions. In this study, the Roman snail 
      (Helix pomatia) Cu-loaded and Cd-loaded isoforms (HpCuMT and HpCdMT) were used as 
      model molecules in order to elucidate the biochemical and evolutionary mechanisms 
      permitting pulmonate MTs to achieve specificity for their cognate metal ion. 
      RESULTS: HpCuMT and HpCdMT were recombinantly synthesized in the presence of 
      Cd(2+), Zn(2+) or Cu(2+) and corresponding metal complexes analysed by 
      electrospray mass spectrometry and circular dichroism (CD) and ultra 
      violet-visible (UV-Vis) spectrophotometry. Both MT isoforms were only able to 
      form unique, homometallic and stable complexes (Cd(6)-HpCdMT and Cu(12)-HpCuMT) 
      with their cognate metal ions. Yeast complementation assays demonstrated that the 
      two isoforms assumed metal-specific functions, in agreement with their binding 
      preferences, in heterologous eukaryotic environments. In the snail organism, the 
      functional metal specificity of HpCdMT and HpCuMT was contributed by 
      metal-specific transcription programming and cell-specific expression. Sequence 
      elucidation and phylogenetic analysis of MT isoforms from a number of snail 
      species revealed that they possess an unspecific and two metal-specific MT 
      isoforms, whose metal specificity was achieved exclusively by evolutionary 
      modulation of non-cysteine amino acid positions. CONCLUSION: The Roman snail 
      HpCdMT and HpCuMT isoforms can thus be regarded as prototypes of isoform families 
      that evolved genuine metal-specificity within pulmonate molluscs. Diversification 
      into these isoforms may have been initiated by gene duplication, followed by 
      speciation and selection towards opposite needs for protecting copper-dominated 
      metabolic pathways from nonessential cadmium. The mechanisms enabling these 
      proteins to be metal-specific could also be relevant for other metalloproteins.
FAU - Palacios, Oscar
AU  - Palacios O
AD  - Departamento Quimica, Faculty Ciencies, Universitat Autonoma de Barcelona, Spain.
FAU - Pagani, Ayelen
AU  - Pagani A
FAU - Perez-Rafael, Silvia
AU  - Perez-Rafael S
FAU - Egg, Margit
AU  - Egg M
FAU - Hockner, Martina
AU  - Hockner M
FAU - Brandstatter, Anita
AU  - Brandstatter A
FAU - Capdevila, Merce
AU  - Capdevila M
FAU - Atrian, Silvia
AU  - Atrian S
FAU - Dallinger, Reinhard
AU  - Dallinger R
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20110121
PL  - England
TA  - BMC Biol
JT  - BMC biology
JID - 101190720
RN  - 00BH33GNGH (Cadmium)
RN  - 789U1901C5 (Copper)
RN  - 9038-94-2 (Metallothionein)
RN  - J41CSQ7QDS (Zinc)
SB  - IM
MH  - Animals
MH  - Cadmium/*metabolism
MH  - Circular Dichroism
MH  - Copper/*metabolism
MH  - Escherichia coli/metabolism
MH  - *Evolution, Molecular
MH  - Gene Duplication
MH  - Helix, Snails/genetics/*metabolism
MH  - Metallothionein/*genetics/*metabolism
MH  - Spectrometry, Mass, Electrospray Ionization
MH  - Spectrophotometry, Ultraviolet
MH  - Yeasts/metabolism
MH  - Zinc/*metabolism
PMC - PMC3033865
EDAT- 2011/01/25 06:00
MHDA- 2011/04/27 06:00
PMCR- 2011/01/21
CRDT- 2011/01/25 06:00
PHST- 2010/12/03 00:00 [received]
PHST- 2011/01/21 00:00 [accepted]
PHST- 2011/01/25 06:00 [entrez]
PHST- 2011/01/25 06:00 [pubmed]
PHST- 2011/04/27 06:00 [medline]
PHST- 2011/01/21 00:00 [pmc-release]
AID - 1741-7007-9-4 [pii]
AID - 10.1186/1741-7007-9-4 [doi]
PST - epublish
SO  - BMC Biol. 2011 Jan 21;9:4. doi: 10.1186/1741-7007-9-4.