Abstract
In all living organisms, transition metals are essential trace elements. Their unique chemical properties are
exploited in metalloenzymes, metalloproteins, and as signaling ions, to perform key biochemical processes.
Integrated metal uptake, distribution, storage, and sensing protein networks guarantee that essential metals are
delivered to their correct targets, while toxic metals are selectively removed from the cellular environment.
Transmembrane metal transporters and interacting metallochaperones are key hubs that selectively regulate the
fluxes of metals across cellular membranes. The chemical, molecular and structural principles that govern metal
transporter cargo selectivity, promiscuity, translocation, and substrate delivery by metallochaperones and
associated metalloproteins are elusive. We developed a strategy that leverages integrated chemical, biophysical,
and structural approaches to determine how metal selection and transport occurs in transporter families featuring
different topologies, transport mechanisms, and energetics. This MIRA application targets the study of primary
active metal pumps, secondary active solute carriers (SLC), and ion facilitators to address: i) the bioinorganic
and coordination chemistry determinants controlling substrate selectivity, affinity, and kinetic lability for rapid
translocation across membranes; ii) how conserved structural frameworks in transporter families are adapted to
diversify cargo specificity towards essential 1st-row and toxic 2nd/3rd-row transition metals; iii) how energy
transduction and conformational changes are coupled to substrate transport; and iv) the chemical,
thermodynamic, kinetic, and structural principles that control metal delivery and uptake to/from transporters by
metallochaperones. The program will target metal transporters involved in metal homeostasis, disease
progression, and pathogen virulence: 1) copper and zinc P-type ATPase pumps and their metallochaperones,
which control copper levels in humans and Cu/Zn concentrations in bacteria acting as virulence factors; 2)
TMEM205, that we discovered as a new human copper/platinum transporter involved in Cu(I)-homeostasis and
anti-cancer Pt-drug resistance, and TMEM52B as its putative chaperone; 3) Fe(II)-selective prokaryotic and
eukaryotic transporters belonging to the IroT, ZIP and CDF families, responsible for iron acquisition and virulence
in pathogens causing bacterial infections and neglected tropical diseases; and 4) prokaryotic nickel and cobalt
transporters controlling essential acquisition of scarce trace elements for Ni/Co enzyme maturation. We will
combine biophysical, spectroscopic, and structural transporter characterization in detergents with the study of
substrate translocation events in real-time in native-like lipid bilayer systems, using the innovative fluorescence
multi-probe platform that we established in our group. We expect to reveal new paradigms underlying transport
kinetics, thermodynamics and mechanism in metal transporters. By targeting neglected aspects of bioinorganic
chemistry in biomedically relevant systems with potential for translational applications, we expect to contribute
to fundamental understanding of metal transport processes across biological membranes in health and disease.
