The serotonin, dopamine, and norepinephrine neurotransmitter transporters (SERT, DAT, and NET, respectively) are involved in a vast array of physical and mental health-related processes ranging from hypertension and heart failure to Parkinson's disease. SERT and DAT are also binding targets of cocaine and amphetamines. Elucidation of the major conformational changes these transporters undergo to regulate the flow of substrate would facilitate the development of pharmacological compounds to combat these ailments by providing an improved understanding of how these complex molecular machines function. SERT, DAT, and NET belong to the neurotransmitter sodium symporter (NSS) family of transporters. Currently, no high resolution structure exists for any member of the NSS family. However, a high resolution crystal structure for the bacterial homolog LeuT has provided insights into the structure and substrate binding of this important transporter family. However, while this crystal structure highlights a single closed- closed state in the transport cycle, multiple other conformations important for function remain unknown. The current work will utilize the NSS homolog LeuT crystal structure and electron paramagnetic resonance (EPR) distance and accessibility data in order to investigate how substrate passage is controlled through conformational changes. To achieve this end, a computational algorithm will be developed which will provide a continuous picture of LeuT as it progresses from one state to another. The second state will be described by the EPR data collected around the gating residues of LeuT. The algorithm will consist of an energy minimization process which is driven by the EPR data to reach the second conformation through a biologically relevant pathway. Such a method will provide a description of how LeuT changes structurally in order to control transport. The structural dynamics determined for LeuT will provide new insights into the homologous transporters of the NSS family. The quality of the dynamic model for LeuT will be validated through additional EPR data collection which will support or refute specific aspects of the prediction. Having a high quality model will allow conclusions for the LeuT system to provide important hypotheses for the NSS family which will be central to understanding the specific conformational motions that are necessary to regulate transport.
Having an improved understanding of how the NSS family regulates transport will facilitate the development of more specific therapeutics. The result will be pharmacological compounds which are potently effective and readily available for a large number of mental and physical diseases.
| Alexander, Nathan S; Preininger, Anita M; Kaya, Ali I et al. (2014) Energetic analysis of the rhodopsin-G-protein complex links the ?5 helix to GDP release. Nat Struct Mol Biol 21:56-63 |
| Kim, Miyeon; Vishnivetskiy, Sergey A; Van Eps, Ned et al. (2012) Conformation of receptor-bound visual arrestin. Proc Natl Acad Sci U S A 109:18407-12 |
| Alexander, Nathan; Woetzel, Nils; Meiler, Jens (2011) bcl::Cluster : A method for clustering biological molecules coupled with visualization in the Pymol Molecular Graphics System. IEEE Int Conf Comput Adv Bio Med Sci 2011:13-18 |
| Kazmier, Kelli; Alexander, Nathan S; Meiler, Jens et al. (2011) Algorithm for selection of optimized EPR distance restraints for de novo protein structure determination. J Struct Biol 173:549-57 |
| Hirst, Stephanie J; Alexander, Nathan; McHaourab, Hassane S et al. (2011) RosettaEPR: an integrated tool for protein structure determination from sparse EPR data. J Struct Biol 173:506-14 |
| Van Eps, Ned; Preininger, Anita M; Alexander, Nathan et al. (2011) Interaction of a G protein with an activated receptor opens the interdomain interface in the alpha subunit. Proc Natl Acad Sci U S A 108:9420-4 |
