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Full-Text Articles in Physical Sciences and Mathematics
The Large Intracellular Loop Of Hzip4 Is An Intrinsically Disordered Zinc Binding Domain, Robert Dempski, Elizabeth Bafaro, Sagar Antala, Tuong-Vi Nguyen, Stephen Dzul, Brian Doyon, Timothy Stemmler
The Large Intracellular Loop Of Hzip4 Is An Intrinsically Disordered Zinc Binding Domain, Robert Dempski, Elizabeth Bafaro, Sagar Antala, Tuong-Vi Nguyen, Stephen Dzul, Brian Doyon, Timothy Stemmler
Robert E. Dempski
The human (h) ZIP4 transporter is a plasma membrane protein which functions to increase the cytosolic concentration of zinc. hZIP4 transports zinc into intestinal cells and therefore has a central role in the absorption of dietary zinc. hZIP4 has eight transmembrane domains and encodes a large intracellular loop between transmembrane domains III and IV, M3M4. Previously, it has been postulated that this domain regulates hZIP4 levels in the plasma membrane in a zinc-dependent manner. The objective of this research was to examine the zinc binding properties of the large intracellular loop of hZIP4. Therefore, we have recombinantly expressed and purified …
The Role Of Histidine Residues In The Specificity Of The Human Zinc Transporter Hzip4, Robert Dempski, Sagar Antala, Elizabeth Bafaro
The Role Of Histidine Residues In The Specificity Of The Human Zinc Transporter Hzip4, Robert Dempski, Sagar Antala, Elizabeth Bafaro
Robert E. Dempski
ZIP transporters, named after the zinc regulated (Zrt) and iron regulated (Irt) transport proteins, are essential for zinc and iron translocation across cellular membranes. These proteins function to increase the cytosolic concentration of transition metals. While both zinc and iron are essential micronutrients which are required for the structure and/or function of hundreds of cellular proteins, the molecular mechanism of ZIP transporters is not well understood. Complicating mechanistic studies is the observation that the concentration of free zinc and iron is nano to picomolar.
Insights Into The Cation Permeation Pathway Of Channelrhodopsin-2, Robert Dempski, Ryan Richards
Insights Into The Cation Permeation Pathway Of Channelrhodopsin-2, Robert Dempski, Ryan Richards
Robert E. Dempski
Channelrhodopsin-2 (ChR2) is a light-activated, non-selective cation channel endogenous to the green algae Chlamydomonas reinhardtii. The unique properties of ChR2 have made it a useful tool in the field of optogenetics. However, the mechanism of ion conductance is not well resolved. Elucidation of the crystal structure of the channelrhodopsin chimera C1C2 has provided structural insight on the putative ChR2 ion conductance pathway. However, it is not clear how the chimeric structure correlates to ChR2 function.
Re-Introduction Of Transmembrane Serine Residues Reduce The Minimum Pore Diameter Of Channelrhodopsin-2, Robert Dempski, Ryan Richards
Re-Introduction Of Transmembrane Serine Residues Reduce The Minimum Pore Diameter Of Channelrhodopsin-2, Robert Dempski, Ryan Richards
Robert E. Dempski
Channelrhodopsin-2 (ChR2) is a microbial-type rhodopsin found in the green algae Chlamydomonas reinhardtii. Under physiological conditions, ChR2 is an inwardly rectifying cation channel that permeates a wide range of mono- and divalent cations. Although this protein shares a high sequence homology with other microbial-type rhodopsins, which are ion pumps, ChR2 is an ion channel. A sequence alignment of ChR2 with bacteriorhodopsin, a proton pump, reveals that ChR2 lacks specific motifs and residues, such as serine and threonine, known to contribute to non-covalent interactions within transmembrane domains. We hypothesized that reintroduction of the eight transmembrane serine residues present in bacteriorhodopsin, but …
The Molecular Determinants Of The Zinc Transporter, Hzip4, Robert Dempski, Sagar Antala, Tuong-Vi Nguyen
The Molecular Determinants Of The Zinc Transporter, Hzip4, Robert Dempski, Sagar Antala, Tuong-Vi Nguyen
Robert E. Dempski
Zinc is an essential micronutrient which is required for the function of hundreds of cellular enzymes. In addition, zinc is the second most abundant transition metal found in biological systems (iron is most abundant). However, the concentration of free zinc is nano to picomolar since most zinc is bound to proteins. This makes investigating the mechanism of zinc transport across the plasma membrane a challenge. Our interest has been to elucidate the mechanism of zinc transport mediated by one member of the ZIP family of proteins, hZIP4.
Ligand-Dependent Effects On The Conformational Equilibrium Of The Na+,K+-Atpase As Monitored By Voltage Clamp Fluorometry, Robert Dempski, Stefan Geys, Ernst Bamberg
Ligand-Dependent Effects On The Conformational Equilibrium Of The Na+,K+-Atpase As Monitored By Voltage Clamp Fluorometry, Robert Dempski, Stefan Geys, Ernst Bamberg
Robert E. Dempski
Voltage clamp fluorometry was used to monitor conformational changes associated with electrogenic partial reactions of the Na(+),K(+)-ATPase after changes in the concentration of internal sodium (Na(+)(i)) or external potassium (K(+)(o)). To probe the effects of the Na(+)(i) concentration on the Na(+) branch of the Na(+),K(+)-ATPase, oocytes were depleted of Na(+)(i) and then loaded with external sodium (Na(+)(o)) using the amiloride-sensitive epithelial sodium channel. The K(+) branch of the Na(+),K(+)-ATPase was studied by exposing the oocytes to different K(+)(o) concentrations in the presence and absence of Na(+)(o) to obtain additional information on the apparent affinity for K(+)(o). Our results demonstrate that …