Structural insight into human Zn(2+)-bound S100A2 from NMR and homology modeling.
The S100 subfamily of EF-hand proteins is distinguished by the binding of Zn(2+) in addition to Ca(2+). In an effort to understand the role of Zn(2+) in modulating the activity of S100 proteins, we have carried out heteronuclear NMR studies of Zn(2+)-bound S100A2 and obtained near complete resonance assignments. This analysis revealed an equilibrium between multiple isoforms due to cis-trans isomerism of proline residues in flexible regions of the protein. The secondary structure of S100A2 has been determined based on the NMR chemical shift index (CSI) technique. The protein is found to possess essentially the same secondary structure found in other S100 proteins such as S100A6 and S100B. Homology models have been built based on the high resolution three-dimensional structures of other S100 proteins. The models predict two Zn(2+) binding clusters, one involving residues His17-Cys21-Cys93 and the other Cys2-His39, and with Cys86 participating in either the N-terminal or the C-terminal binding site.
Randazzo
A
A
Department of Biochemistry, Center for Structural Biology, Vanderbilt University, 896 MRB II, Nashville, TN 37232-0146, USA.
Acklin
C
C
Schäfer
B W
BW
Heizmann
C W
CW
Chazin
W J
WJ
D002135:Calcium-Binding Proteins / Q000737:chemistry; D002352:Carrier Proteins / Q000737:chemistry; D018797:Cell Cycle Proteins; D002630:Chemotactic Factors / Q000737:chemistry*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D009414:Nerve Growth Factors / Q000737:chemistry; D011487:Protein Conformation; D015203:Reproducibility of Results; D000075383:S100 Calcium Binding Protein A6; D000075023:S100 Calcium Binding Protein A7; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid; D015032:Zinc / Q000737:chemistry*
D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002630:Chemotactic Factors; D009414:Nerve Growth Factors; D000075383:S100 Calcium Binding Protein A6; D000075023:S100 Calcium Binding Protein A7; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins; C098997:S100A2 protein, human; C089242:S100A7 protein, human; C579160:S100B protein, human; C017800:zinc-binding protein; C055351:S100A6 protein, human; D015032:Zinc