IGEM:MIT/2007/Heavy Metals

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**The motif (CGCCG)3 was found to bind both cadmium and mercury (see Pazirandeh98)
**The motif (CGCCG)3 was found to bind both cadmium and mercury (see Pazirandeh98)
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*The full Pazirandeh98 binding sequence (CGCCG) is:  CGCCGKGHCGCCGKGHCGCCG
 
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*From DeSilva02, the MerP-derived Hg binding (very specific) sequence (GMTCCAA) could be repeated 3x
 
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*For cadmium binding, could use the CadA-derived sequence (GFTCANC)
 
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*Alpha domain of Human MT-II is:  CCSCCPVGCAKCAQGCICKGASDKCSCCA
 
 +
==Binding Sequences To Try==
 +
*The full Pazirandeh98 Hg/Cd-specific binding sequence (CGCCG) is:  CGCCGKGHCGCCGKGHCGCCG
 +
*From DeSilva02, the MerP-derived Hg-specific binding sequence (GMTCCAA) could be repeated 3x:  GMTCCAAGMTCCAAGMTCCAA
 +
*For good non-specific binding, best bet seems to be alpha domain of Human MT-II is:  CCSCCPVGCAKCAQGCICKGASDKCSCCA
 +
*For Cd-specific binding, could use the CadA-derived sequence (GFTCANC)
Seems that Mejare01 does a nice job of comparing the different Cd-binding methods which have been tried.  According to them, the methods which gave the biggest increase (>60-fold) in binding capacity were those that expressed entire MT proteins (or domains of them).   
Seems that Mejare01 does a nice job of comparing the different Cd-binding methods which have been tried.  According to them, the methods which gave the biggest increase (>60-fold) in binding capacity were those that expressed entire MT proteins (or domains of them).   

Revision as of 16:53, 13 July 2007

Contents

Reviews

  • Excellent Summary of Bacterial Metal Resistance (a must read)
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  1. Error fetching PMID 16133099: [Silver05]
  • A Good Overview on Pollution (though slightly back-dated): Quantitative assessment of worldwide contamination of air, water and soil by trace metals [1]
  • A summary of Pollutants from the EPA [2]
  • Review Papers on Bioremediation
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  1. Error fetching PMID 15734556: [Paul05]
  2. Error fetching PMID 12413663: [Valls02]
  3. Error fetching PMID 10702338: [Bruins00]
All Medline abstracts: PubMed HubMed
  • Paul - discusses advantages/disadvantages/problems of bioremediation
  • Bruins, Valls - discusses various kinds of bioremediation systems

Heavy Metal Binding Proteins/Peptides

There are several classes of metal binding proteins to consider. (for review, see Cobbett02, below)

First, those that bind to many metal types (Cd, Hg, Pb, Cu, Zn, etc). These are nice in that they are multifunctional, but the disadvantage is that they will also bind non-toxic ions like Zn, thus decreasing their efficiency.

    • Metallothioneins (MT's) -- small animal proteins which contain many cysteine motifs (usually CxxC)
    • Phytochelatins (PC's) -- plant peptides of the form (EC)n-G where n=# repeats (usually 2-10, but can be as many as 20) (see the Bae papers)

Also, certain artificially selected sequences bind selectively to certain metals.

    • The MT-like motif CCAA was found to highly selective for Hg, while CAAC had broad specificity (see DeSilva02)
    • The motif (CGCCG)3 was found to bind both cadmium and mercury (see Pazirandeh98)


Binding Sequences To Try

  • The full Pazirandeh98 Hg/Cd-specific binding sequence (CGCCG) is: CGCCGKGHCGCCGKGHCGCCG
  • From DeSilva02, the MerP-derived Hg-specific binding sequence (GMTCCAA) could be repeated 3x: GMTCCAAGMTCCAAGMTCCAA
  • For good non-specific binding, best bet seems to be alpha domain of Human MT-II is: CCSCCPVGCAKCAQGCICKGASDKCSCCA
  • For Cd-specific binding, could use the CadA-derived sequence (GFTCANC)

Seems that Mejare01 does a nice job of comparing the different Cd-binding methods which have been tried. According to them, the methods which gave the biggest increase (>60-fold) in binding capacity were those that expressed entire MT proteins (or domains of them).


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  2. Error fetching PMID 9758845: [Biosorbants]
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  4. Error fetching PMID 11164556: [Mejare01]
  5. Error fetching PMID 11710062: [Lu01]
  6. Error fetching PMID 11042548: [Bae00]
  7. Error fetching PMID 11679366: [Bae01]
  8. Error fetching PMID 11803043: [Bae02]
  9. Error fetching PMID 10071794: [Kotrba99b]
  10. Error fetching PMID 12115136: [Desilva02]
  11. Error fetching PMID 12039007: [Opella02]
  12. Error fetching PMID 9573175: [Sousa98]
  13. Error fetching PMID 10736021: [Mauro00]
  14. Error fetching PMID 12221971: [Cobbett02]
  15. Error fetching PMID 9758845: [Pazirandeh98]
All Medline abstracts: PubMed HubMed

Cadmium

Summary

  • Cd causes damage to cells primarily by the generation of reactive oxygen species (ROS), which causes single-strand DNA damage and disrupts the synthesis of nucleic acids and proteins. Cd is also an inhibitor of the DNA mismatch repair system…Results of this study confirmed that Cd toxicity caused profound changes in gene expression in which several stress response systems were induced simultaneously.
  • known carcinogen
  • Most recent(June06) paper on e.coli bioaccumulation of Cd
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  1. Error fetching PMID 16890348: [Deng06]

Contamination Levels/Limits

  • MCL(Maximum Containment Level): 5 ppb
  • MCLG(Maximum Containment Level Goal): 5 ppb
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  2. Error fetching PMID 12505433: [Satarug03]
All Medline abstracts: PubMed HubMed


Cadmium Contamination Sites

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Plachimada, India: [3]
    • statistics on Pb, Cd, Cr levels in well water surrounding a Coca-Cola plant (2006)
    • pictures too :)


Promoters

Pubmed: Plasmid pI258 (from S.aureus) cadmium resistance (cadA) gene, complete cds [4]

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  1. Error fetching PMID 12901859: [Brocklehurst03]
  • Brocklehurst - contains sequence for ZntR/CadR and PzntA/PcadA
    • Semmie's article on CadC linked with GFP [5]

Mercury

Contamination Levels/Limits

  • MCL: 2 ppb
  • MCLG: 2 ppb
  • 20 ppb makes the fish mercury buildup significant

Polluted sites

  • Onondaga lake [6] [7] [8]
  • Salt Plains National Wildlife Refuge [9]

Detection (to assess our system)


Promoter

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  2. Error fetching PMID 1312997: [Park92]
  3. Error fetching PMID 1334070: [Condee92]
  4. Error fetching PMID 4092936: [Gambill85]
  5. Error fetching PMID 11094290: [Hansen00]
All Medline abstracts: PubMed HubMed
  • Condee - Contains sequence for merO/P region
  • Hansen - Plasmid with Pmer, MerR, and reporter (lux, lac, or gfp) tested in e.coli

Sponge

  • Accumulation of Hg ions in cell membrane [10]

Current Industry Filtration Techniques

Mercury: approved by EPA - Coagulation/Filtration; Granular Activated Carbon; Lime softening; Reverse osmosis.

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