structural-biology-2017-scientifictracks-abstracts

Page 139

Notes:

conferenceseries

.com

Volume 10, Issue 8 (Suppl)

J Proteomics Bioinform, an open access journal

ISSN: 0974-276X

Structural Biology 2017

September 18-20, 2017

International Conference on

Structural Biology

September 18-20, 2017 Zurich, Switzerland

Jessica L Thomaston, J Proteomics Bioinform 2017, 10:8(Suppl)

DOI: 10.4172/0974-276X-C1-0100

XFELstructures of the M2 proton channel of influenzaAreveal pH-dependent water networks under

room temperature conditions

Jessica L Thomaston,

University of California, San Francisco, USA

he M2 proton channel of influenza A is a drug target that is essential for replication of the flu virus. It is also a model

system for the study of selective, unidirectional proton transport across a membrane. Ordered water molecules arranged in

wires inside the channel pore have been proposed to play a role in the conduction of protons to the four gating His37 residues

and the stabilization of multiple positive charges within the channel. Previous crystallographic structures determined using

a synchrotron radiation source were biased by cryogenic data collection conditions, and room-temperature data collection

was limited by radiation damage. These problems have been avoided through room temperature diffraction at an X-ray free

electron laser. Data were collected at an XFEL source to a resolution of 1.4 Å at three different pH conditions: pH 5.5, pH 6.5,

and pH 8.0. Here, we examine the ordering of water in the M2 pore within crystals containing only the C

open

conformation,

which is an intermediate that accumulates at high protonation of the His37 tetrad. This allows us to access multiple protonation

states of His37 in the C

open

conformation and probe changes in solvent ordering prior to and following the release of a proton

into the viral interior. At pH 5.5, a continuous hydrogen bonded network of water molecules spans the vertical length of the

channel, consistent with a Grotthuss mechanism model for proton transport to the His37 tetrad. This ordered solvent at pH

5.5 could act to stabilize the positive charges that build up on the gating His37 tetrad during the proton conduction cycle. The

number of ordered pore waters decreases at higher pH, where the C

open

state is less stable. These studies provide a graphical

view of the response of water to a change in charge within a restricted channel environment.

Biography

Jessica L Thomaston is a PhD candidate in the lab of Professor William DeGrado at the University of California, San Francisco. She studies the structure of the

influenza M2 proton using lipidic cubic phase crystallization techniques and x-ray diffraction at synchrotron and XFEL sources. The M2 protein is among the smallest

proton channels found in nature and is also a drug target against the flu. Her work focuses on the proton conduction mechanism of the M2 channel, particularly

the involvement of water in proton transport and the structural characterization of how drugs and novel inhibitors bind to the channel and block proton conduction.

jessica.thomaston@ucsf.edu

Figure1:

Room temperature XFEL structures of the M2 proton

channel transmembrane domain at pH 5.5, 6.5, and 8.0. Solvent

ordering is at a maximum at pH 5.5, with fewer ordered waters

at pH 6.5 and pH 8.0. A continuous hydrogen bonding network is

observed in the low pH condition and could be consistent with a

Grotthuss transport mechanism for proton transport when the

channel is at maximally conducting pH conditions.