My Work

I am a Scientist. Specifically I work in structural biology. This means that I apply biochemical and biophysical techniques to study the structures of protein molecules. The proteins that I study are embedded within the cell membranes and are therefore known as membrane proteins. In order to solve their structures I apply both X-ray crystallography and electron cryo-microscopy (cryo-EM). These techniques require purified samples of protein and most of my time is spent figuring out how to purify sufficient amounts of these proteins for the structural work.

Currently I am a Marie Skłodowska-Curie fellow at the Institute of Science and Technology (IST) Austria, in Klosterneuberg (near Vienna) in the lab of Dr. Leonid Sazanov. Here I am working on two main projects: 1) the characterization of mammalian mitochondrial complex I of the electron transport chain and 2) the characterization of respiratory supercomplexes.

When I started my postdoc it was as a MRC Career Development Fellow at the MRC Mitochondrial Biology Unit in Cambridge, UK. There I was studying the structure and function of the Nicotinamide Nucleotide Transhydrogenase (NNT), an important mitochondrial protein complex that sits at the interface of anabolism, catabolism and the proton motive force. However, I quickly changed projects and the lab moved to Austria.

In September 2013 I defended my PhD in the Laboratory of Molecular Neurobiology and Biophysics at The Rockefeller University in New York. My PhD adviser was Rod MacKinnon, so we normally just call it the MacKinnon Lab. I worked on the biophysics of ion channels; specifically, my project was to structurally and functionally characterize the voltage-gated ion channel Hv. I will definitely be writing lots about Hv so I won’t say too much more about it here.

Watch me defend my thesis! Check out this recording of the public lecture portion of my thesis defense. Introduction by Rod MacKinnon.

I am from the west coast of Canada. I was born in Surrey B.C. and grew up in Kamloops and Victoria. I did my undergrad at the University of Victoria where I got my first taste of research. As a work/study student in Dr. Stephen Evans’ Lab, I studied the structure of the human ABO(H) blood group glycosyltransferases. These enzymes are responsible for catalyzing the addition of the final carbohydrate moiety to the H-antigen.

Below is a selected list of my publications. For a complete list please check out my ReseachGate profile.
James A. Letts

Functional reconstitution of purified human Hv1 H(+) channels.

Seok-Yong Lee*, James A Letts*, Roderick MacKinnon

*Equal Contributors

Journal Article: Journal of Molecular Biology. 03/2009; DOI: 10.1016/j.jmb.2009.02.034

Voltage-dependent H(+) (Hv) channels mediate proton conduction into and out of cells under the control of membrane voltage. Hv channels are unusual compared to voltage-dependent K(+), Na(+) and Ca(2+) channels in that Hv channel genes encode a voltage sensor domain (VSD) without a pore domain. The H(+) currents observed when Hv channels are expressed heterologously suggest that the VSD itself provides the pathway for proton conduction. In order to exclude the possibility that the Hv channel VSD assembles with an as yet unknown protein in the cell membrane as a requirement for H(+) conduction we have purified Hv channels to homogeneity and reconstituted them into synthetic lipid liposomes. The Hv channel VSD by itself supports H(+) flux.

Dimeric subunit stoichiometry of the human voltage-dependent proton channel Hv1.

Seok-Yong Lee, James A Letts, Roderick MacKinnon

Journal Article: Proceedings of the National Academy of Sciences. 07/2008; 105(22):7692-5. DOI: 10.1073/pnas.0803277105

In voltage-gated Na(+), K(+), and Ca(2+) channels, four voltage-sensor domains operate on a central pore domain in response to membrane voltage. In contrast, the voltage-gated proton channel (Hv) contains only a voltage-sensor domain, lacking a separate pore domain. The subunit stoichiometry and organization of Hv has been unknown. Here, we show that human Hv1 forms a dimer in the membrane and define regions that are close to the dimer interface by using cysteine cross-linking. Two dimeric interfaces appear to exist in Hv1, one mediated by S1 and the adjacent extracellular loop, and the other mediated by a putative intracellular coiled-coil domain. It may be significant that Hv1 uses for its dimer interface a surface that corresponds to the interface between the voltage sensor and pore in Kv channels.
Comments
3 Responses to “My Work”
  1. congrats on your recent pnas paper – nicely done!

  2. Congrats…really impressive amount of work…amazed at how recalcitrant some of these VSDs can be! good luck with your postdoc work.

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