Specificity and Zn2+ enhancement of the S100B binding epitope TRTK-12.
The calcium-binding protein S100B (an S100 dimer composed of two S100beta monomers) is proposed to act as a calcium-sensory protein through interactions with a variety of proteins. While the nature of the exact targets for S100B has yet to be defined, random bacteriophage peptide mapping experiments have elucidated a calcium-sensitive "epitope" (TRTK-12) for S100B recognition. In this work, interactions of TRTK-12 with S100B have been shown to be calcium-sensitive. In addition, the interactions are enhanced by zinc binding to S100B, resulting in an approximate 5-fold decrease in the TRTK-12/S100B dissociation constant. Moreover, Zn2+ binding alone has little effect. TRTK-12 showed little evidence for binding to another S100 protein, S100A11 or to a peptide derived from the N terminus of S100B, indicating both a level of specificity for TRTK-12 recognition by S100B and that the N-terminal region of S100B is probably not involved in protein-protein interactions. NMR spectroscopy revealed residues most responsive to TRTK-12 binding that could be mapped to the surface of the three-dimensional structure of calcium-saturated S100B, revealing a common region indicative of a binding site.
Barber
K R
KR
Department of Biochemistry and McLaughlin Macromolecular Structure Facility, University of Western Ontario, London, Ontario N6A 5C1, Canada.
McClintock
K A
KA
Jamieson
G A
GA
Dimlich
R V
RV
Shaw
G S
GS
D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism; D019281:Dimerization; D006801:Humans; D008274:Magnesium / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009414:Nerve Growth Factors; D010449:Peptide Mapping; D011487:Protein Conformation; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D015032:Zinc / Q000378:metabolism*
D009414:Nerve Growth Factors; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins; C579160:S100B protein, human; C072337:S100A11 protein, human; D008274:Magnesium; D015032:Zinc; D002118:Calcium