Structural characterization of synaptotagmin I
dc.contributor.advisor | Andres Oberhauser | en_US |
dc.contributor.committeeMember | Xiaodong Cheng | en_US |
dc.contributor.committeeMember | R. Bryan Sutton | en_US |
dc.contributor.committeeMember | Mark Hellmich | en_US |
dc.contributor.committeeMember | Darren Boehning | en_US |
dc.creator | Kerry Fuson | en_US |
dc.date.accessioned | 2011-12-20T16:04:38Z | |
dc.date.accessioned | 2014-02-19T22:05:06Z | |
dc.date.available | 2010-09-28 | en_US |
dc.date.available | 2011-12-20T16:04:38Z | |
dc.date.available | 2014-02-19T22:05:06Z | |
dc.date.created | 2009-04-15 | en_US |
dc.date.issued | 2009-02-13 | en_US |
dc.description.abstract | Synaptotagmin I is the most abundant Ca+2 binding protein present on synaptic vesicles accounting for 7% of total vesicle protein and is widely accepted as the Ca2+ sensor in fast synchronous neurotransmitter release. The protein is composed of one trans-membrane domain, an unstructured linker followed by two C2A domains identified as C2A and C2B. Each C2 domain is composed of an 8 stranded β-sandwich joined by a 9 amino acid linker. The Ca+2 binding pocket is composed of three loops located at the apex of the protein. In the Syt I C2AB structure, we see evidence of a domain structural change in the absence of Ca2+. Analysis of interacting residues between C2A and C2B show a network of highly conserved residues within the C2 domain that regulates Ca+2/phohspholipid binding in C2A. Analysis of the Syt I C2A structure, as well as, previous C2A structures shows a strong H-bond between Tyr 180 and His 237 in C2A. By removing this H-bond, disorder of Loop 3 is increased and the thermodynamic stability of the C2 domain decreases. Our hypothesis is that the absolute position of the Ca2+ binding loops of C2 domains affects Ca+2 affinity and, and ultimately domain stability. We used several different biochemical approaches to test the hypothesis. We assessed the importance of Loop 3 mutations using X-ray crystallography methods, bulk thermodynamic measurements using lifetime fluorescence, and analyzed the mechanical properties of the C2-domains using single molecule force spectroscopy.\r\nWe studied the mechanical stability of the C2A and C2B domains of human Syt1 using single-molecule atomic force microscopy. We found that stretching the C2AB domains of Syt1 resulted in two distinct unfolding force peaks. The larger force peak of ~100pN was identified as C2B and the second peak of ~50pN as C2A. Further, a significant fraction of C2A domains unfolded through a low force intermediate that was not observed in C2B. We conclude that these domains have different mechanical properties. We hypothesize that a relatively small stretching force may be sufficient to deform the effector-binding regions of C2A domain and modulate the affinity for SNAREs, phospholipids and Ca+2.\r\n | en_US |
dc.format.medium | electronic | en_US |
dc.identifier.other | etd-04152009-130217 | en_US |
dc.identifier.uri | http://hdl.handle.net/2152.3/98 | |
dc.language.iso | eng | en_US |
dc.rights | Copyright © is held by the author. Presentation of this material on the TDL web site by The University of Texas Medical Branch at Galveston was made possible under a limited license grant from the author who has retained all copyrights in the works. | en_US |
dc.subject | X-ray crystallography | en_US |
dc.subject | synaptotagmin | en_US |
dc.subject | protein structure | en_US |
dc.subject | exocytosis | en_US |
dc.title | Structural characterization of synaptotagmin I | en_US |
dc.type.genre | dissertation | en_US |
dc.type.material | text | en_US |
thesis.degree.department | Human Biological Chemistry and Genetics | en_US |
thesis.degree.grantor | The University of Texas Medical Branch | en_US |
thesis.degree.level | Doctoral | en_US |
thesis.degree.name | PhD | en_US |