Crystallographic identification of Ca2+ and Sr2+ coordination sites in synaptotagmin I C2B domain Journal Article
| Authors: | Cheng, Y.; Sequeira, S. M.; Malinina, L.; Terechko, V.; Söllner, T. H.; Patel, D. J. |
| Article Title: | Crystallographic identification of Ca2+ and Sr2+ coordination sites in synaptotagmin I C2B domain |
| Abstract: | Synaptotagmin I has two tandem Ca2+-binding C2 domains, which are essential for fast synchronous synaptic transmission in the central nervous system. We have solved four crystal structures of the C 2B domain, one of them in the cation-free form at 1.50 Å resolution, two in the Ca2+-bound form at 1.04 Å (two bound Ca2+ ions) and 1.65 Å (three bound Ca2+ ions) resolution and one in the Sr2+-bound form at 1.18 Å (one bound Sr2+ ion) resolution. The side chains of four highly conserved aspartic acids (D303, D309, D363, and D365) and two main chain oxygens (M302:O and Y364:O), together with water molecules, are in direct contact with two bound Ca2+ ions (sites 1 and 2). At higher Ca2+ concentrations, the side chain of N333 rotates and cooperates with D309 to generate a third Ca2+ coordination site (site 3). Divalent cation binding sites 1 and 2 in the C2B domain were previously identified from NMR NOE patterns and titration studies, supplemented by site-directed mutation analysis. One difference between the crystal and NMR studies involves D371, which is not involved in coordination with any of the identified Ca2+ sites in the crystal structures, while it is coordinated to Ca2+ in site 2 in the NMR structure. In the presence of Sr2+, which is also capable of triggering exocytosis, but with lower efficiency, only one cation binding site (site 1) was occupied in the crystallographic structure. |
| Keywords: | unclassified drug; nonhuman; molecular genetics; binding affinity; protein domain; protein motif; animal; animals; oxygen; nerve tissue proteins; calcium; mutational analysis; chemistry; amino acid sequence; molecular sequence data; sequence alignment; membrane glycoproteins; nucleotide sequence; membrane protein; rat; nuclear magnetic resonance spectroscopy; binding site; crystal structure; crystallography, x-ray; protein structure, tertiary; binding sites; rats; calcium binding protein; calcium-binding proteins; molecular interaction; conformational transition; protein structure; structure analysis; x ray crystallography; site directed mutagenesis; nerve protein; protein tertiary structure; aspartic acid; concentration response; synaptotagmin; structural homology, protein; x-ray crystallography; structural homology; exocytosis; divalent cation; cation; synaptotagmin i; synaptic transmission; rotation; titrimetry; nuclear overhauser effect; cations; strontium; priority journal; article; c2b domain; calcium binding; strontium binding; syt1 protein, rat; ef hand motifs; synaptotagmins |
| Journal Title: | Protein Science |
| Volume: | 13 |
| Issue: | 10 |
| ISSN: | 0961-8368 |
| Publisher: | Wiley Blackwell |
| Date Published: | 2004-10-01 |
| Start Page: | 2665 |
| End Page: | 2672 |
| Language: | English |
| DOI: | 10.1110/ps.04832604 |
| PROVIDER: | scopus |
| PMCID: | PMC2286539 |
| PUBMED: | 15340165 |
| DOI/URL: | |
| Notes: | Protein Sci. -- Cited By (since 1996):32 -- Export Date: 16 June 2014 -- CODEN: PRCIE -- Molecular Sequence Numbers: GENBANK: AAA87724, AAA87725, P21707, P29101, P40748, P47861, P50232; -- Source: Scopus |
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