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JBS Halo Kits

The search for suitable heavy-atom derivatives can be quite tedious and binding of heavy atoms often results in disrupting the crystal lattice. Halogenated ATP and GTP analogs however, provide an alternative method that allows rational incorporation of heavy atoms into a large number of physiologically relevant enzymes:

  • In the human genome alone, estimated 5,000 to 10,000 proteins interact with ATP or GTP, e.g. protein and nucleotide kinases, motor proteins, chaperones or the superfamily of GTPases, respectively.
  • The incorporation of iodine or bromine allows MIR or MAD phasing for proteins with molecular weights of at least up to 50 kDa. Importantly, for MIR experiments, such derivatives are likely to be isomorphous to the native crystals
  • The binding kinetics of 2'-halogenated ATP analogs to most enzymes so far investigated (including myosin, creatine kinase, hexokinase, pyruvate kinase and UMP/CMP kinase) are similar to those of non-substituted ATP.
  • The complexes of 2'-halogenated GTP analogs with the GTPases p21ras or Rab5 have dissociation constants well suitable for crystallization.
  • Several proteins including kinesin, non-claret disjunctional protein and TMP kinase have been sucessfully crystallized with 2'-halogenated analogs.

JBS Halo-ATP Kit

The JBS Halo-ATP Kit contains 8 halogenated Adenosine nucleotides (5 nmol as lyophilized sodium salts):

  • 2'-Iodo-dADP, 2'-Iodo-dATP
  • 2'-Bromo-dADP, 2'-Bromo-dATP
  • 8-Iodo-ADP, 8-Iodo-ATP
  • 8-Bromo-ADP, 8-Bromo-ATP

JBS Halo-GTP Kit

The JBS Halo-GTP Kit contains 4 halogenated Guanosine nucleotides (5 nmol as lyophilized sodium salts):

  • 8-Iodo-GDP, 8-Iodo-GTP
  • 8-Bromo-GDP, 8-Bromo-GTP

The protein under investigation can either be co-crystallized with the respective analog, or the nucleotide can be added directly to the crystallization drops containing pre-grown crystals. Since it is difficult to predict a priori which one of the Halo-nucleotides will give the highest quality derivative crystals, it is advisable to screen them all in parallel.

Co-crystals of human TMP-kinase and 2'Br-ADP/ATP

Selected References

Gruen et al. (1999) 2'-Halo-ATP and -GTP analogues: Rational phasing tools for protein crystallography. Protein Sci. 8:2524.
Gruen et al. (1999) Synthesis of 2'-iodo- and 2'-bromo-ATP and GTP analogues as potential phasing tools for X-ray crystallography. Nucleos. Nucleot. 18 (1):137.
Naber et al. (1995) A novel adenosine-triphosphate analog with a heavy-atom to target the nucleotide-binding site of proteins. Protein Sci. 4:1824.