3 research outputs found
Antigenic Peptide Recognition on the Human ABC Transporter TAP Resolved by DNP-Enhanced Solid-State NMR Spectroscopy
The human transporter
associated with antigen processing (TAP)
is a 150 kDa heterodimeric ABC transport complex that selects peptides
for export into the endoplasmic reticulum and subsequent loading onto
major histocompatibility complex class I molecules to trigger adaptive
immune responses against virally or malignantly transformed cells.
To date, no atomic-resolution information on peptideāTAP interactions
has been obtained, hampering a mechanistic understanding of the early
steps of substrate translocation catalyzed by TAP. Here, we developed
a mild method to concentrate an unstable membrane protein complex
and combined this effort with dynamic nuclear polarization enhanced
magic angle spinning solid-state NMR to study this challenging membrane
proteināsubstrate complex. We were able to determine the atomic-resolution
backbone conformation of an antigenic peptide bound to human TAP.
Our NMR data also provide unparalleled insights into the nature of
the interactions between the side chains of the antigen peptide and
TAP. By combining NMR data and molecular modeling, the location of
the peptide binding cavity has been identified, revealing a complex
scenario of peptideāTAP recognition. Our findings reveal a
structural and chemical basis of substrate selection rules, which
define the crucial function of this ABC transporter in human immunity
and health. This work is the first NMR study of a eukaryotic transporter
protein and presents the power of solid-state NMR in this growing
field
HostāGuest Complexes as Water-Soluble High-Performance DNP Polarizing Agents
Dynamic
nuclear polarization (DNP) enhances the sensitivity of
solid-state NMR (SSNMR) spectroscopy by orders of magnitude and, therefore,
opens possibilities for novel applications from biology to materials
science. This multitude of opportunities implicates a need for high-performance
polarizing agents, which integrate specific physical and chemical
features tailored for various applications. Here, we demonstrate that
for the biradical bTbK in complex with captisol (CAP), a Ī²-cyclodextrin
derivative, hostāguest assembling offers a new and easily accessible
approach for the development of new polarizing agents. In contrast
to bTbK, the CAP-bTbK complex is water-soluble and shows significantly
improved DNP performance compared to the commonly used DNP agent TOTAPOL.
Furthermore, NMR and EPR data reveal improved electron and nuclear
spin relaxation properties for bTbK within the host molecule. The
numerous possibilities to functionalize host molecules will permit
designing novel radical complexes targeting diverse applications
Interaction of Cisplatin with Human Superoxide Dismutase
<i>cis</i>-DiamminedichloroplatinumĀ(II) (cisplatin)
is
able to interact with human superoxide dismutase (hSOD1) in the disulfide
oxidized apo form with a dissociation constant of 37 Ā± 3 Ī¼M
through binding cysteine 111 (Cys111) located at the edge of the subunit
interface. It also binds to Cu<sub>2</sub>āZn<sub>2</sub> and
Zn<sub>2</sub>āZn<sub>2</sub> forms of hSOD1. Cisplatin inhibits
aggregation of demetalated oxidized hSOD1, and it is further able
to dissolve and monomerize oxidized hSOD1 oligomers <i>in vitro</i> and <i>in cell</i>, thus indicating its potential as a
leading compound for amyotrophic lateral sclerosis