These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: An examination of glutamic acid in the -X chelating position of the helix-loop-helix calcium binding motif.
    Author: Procyshyn RM, Reid RE.
    Journal: Arch Biochem Biophys; 1994 Jun; 311(2):425-9. PubMed ID: 7911293.
    Abstract:
    Poor calcium affinity was exhibited in helix-loop-helix calcium binding motifs with X-axis acid pairs containing aspartic acid in the -X chelating position. In order to increase interaction of the -X chelating residue with the cation, helix-loop-helix calcium binding motifs were synthesized containing three and four acid residues in chelating positions, with a glutamic acid replacing aspartic acid in the -X chelating position. The glutamate-containing motif gave an unexpected 6-fold decrease in cation affinity for the three-acid residue loop motif (KCa = 524 microM vs KCa = 3140 microM) and a 46-fold decrease for the four-acid residue loop motif (KCa = 42.1 microM vs KCa 1950 microM). To improve calcium binding of the glutamate-containing motifs, peptides were synthesized keeping glutamate in the -X position and inserting serine in the +Z position to provide a hydrogen-bonded system stabilizing the glutamate interaction with the cation. The serine residue further reduced calcium affinity in both the three-acid residue loop (KCa = 19.6 mM) and the four-acid residue loop (KCa = 2806 microM). These results indicate that glutamate and serine residues in the -X and +Z positions, respectively, can be detrimental to calcium binding. However, in natural calcium binding proteins, glutamate in the -X chelating position can confer high affinity for calcium in helix-loop-helix calcium binding motifs, but this may be dependent on the environment created by as yet undetermined factors.
    [Abstract] [Full Text] [Related] [New Search]