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.com
Volume 10, Issue 8 (Suppl)
J Proteomics Bioinform, an open access journal
ISSN: 0974-276X
Structural Biology 2017
September 18-20, 2017
9
th
International Conference on
Structural Biology
September 18-20, 2017 Zurich, Switzerland
Structural basis of sodium/citrate symporter as a secondary transporter
Mi Sun Jin
1
, Ji Won Kim
2
, Subin Kim
1
, Haerim Lee
2
, Songwon Kim
1
and
Jie-Oh Lee
2
1
Gwangju Institute of Science and Technology, South Korea
2
KAIST, South Korea
T
he sodium-dependent citrate transporter of
Klebsiella pneumoniae
(
Kp
CitS) belongs to the 2-hydroxycarboxylate
transporter (2-HCT) family and allows the cell to use citrate as sole carbon and energy source in anaerobic conditions. We
present crystal structures of
Kp
CitS in its citrate-bound outward-facing as well as citrate-free inward-facing state. The structure
of the asymmetric
Kp
CitS homodimer containing both outward- and inward-open protomers was also determined. The
structures reveal that the
Kp
CitS dimerization domain remains stationary throughout the transport cycle due to an extensive
hydrogen bond network as well as hydrophobic interactions. In contrast, its transport domain undergoes a ~35° rigid-body
rotation and a ~17 Å translocation perpendicular to the membrane to expose the substrate-binding site alternately to either
side of the membrane. Homology models of two other 2-HCT proteins based on the
Kp
CitS structure offer structural insights
into their differences in substrate specificity at a molecular level. On the basis of our results and previous biochemical data,
we propose that the activity of the 2-HCT family of transporters involves an elevator-like movement in which the transport
domain itself traverses the lipid bilayer, carrying the substrate into the cell in a sodium-dependent manner.
Biography
Mi Sun Jin is an Assistant Professor in School of Life Sciences, GIST since 2014. She completed BS in 2002 from Sogang University, MS in 2004 from KAIST, and
PhD in 2008 from KAIST (under the supervision of Jie-Oh Lee). She held two Postdoctoral Fellowships; one from 2008-2009 at KAIST (Advisor: Jie-Oh Lee), and
other from 2009-2013 from Purdue University (Advisor: Jue Chen). From 2013 to 2014, he worked as Research Specialist in Purdue University.
misunjin@gist.ac.krMi Sun Jin et al., J Proteomics Bioinform 2017, 10:8(Suppl)
DOI: 10.4172/0974-276X-C1-0100