Biomedical subjects

Paul B Card

Publications and source records attributed to Paul B Card.

3 recordsLinked to original sources

PubMed2005

Structural basis of ARNT PAS-B dimerization: use of a common beta-sheet interface for hetero- and homodimerization.

The aryl hydrocarbon receptor nuclear translocator (ARNT) is a promiscuous bHLH-PAS (Per-ARNT-Sim) protein that forms heterodimeric transcriptional regulator complexes with several other bHLH-PAS subunits to control a variety of biological pathways, some of which are centrally involved in disease initiation and/or progression. One of these is the hypoxia response pathway, which allows eukaryotic cells to respond to low oxygen tension via the formation of a heterodimeric complex between ARNT and another bHLH-PAS protein, the hypoxia-inducible factor alpha (HIF-alpha). We have previously shown that the C-terminal PAS domains of an HIF-alpha isoform (HIF-2alpha) and ARNT interact in vitro, and that mutations in the solvent-exposed beta-sheet surface of the HIF-2alpha domain not only disrupt this interaction, but also greatly attenuate the hypoxia response in living cells. Here, we have solved the solution structure of the corresponding PAS domain of ARNT and show that it utilizes a very similar interface for the interaction with the HIF-2alpha PAS domain. We also show that this domain self-associates in a concentration-dependent manner, and that the interface used in this homodimeric complex is very similar to that used in the formation of heterodimer. In addition, using experimentally derived NMR restraints, we used the program HADDOCK to calculate a low-resolution model of the complex formed in solution by these two PAS domains, and confirm the validity of this model using site-directed spin labeling to obtain long-range distance information in solution. With this information, we propose a model for the mode of multi-PAS domain interaction in bHLH-PAS transcriptional activation complexes.

Aryl Hydrocarbon Receptor Nuclear Translocator↗

PubMed2005

Identification and optimization of protein domains for NMR studies.

The success of genomic sequencing projects in recent years has presented protein scientists with a formidable challenge in characterizing the vast number of gene products that have subsequently been identified. NMR has proven to be a valuable tool in the elucidation of various properties for many of these proteins, allowing versatile studies of structure, dynamics, and interactions in the solution state. But the characteristics needed for proteins amenable to this kind of study, such as folding capability, long-term stability, and high solubility, require robust and expeditious methods for the identification and optimization of target protein domains. Here we present a variety of computational and experimental methods developed for these purposes and show that great care must often be taken in the design of constructs intended for NMR-based investigations.

Deuterium Exchange Measurement↗

PubMed2003

Structural basis for PAS domain heterodimerization in the basic helix--loop--helix-PAS transcription factor hypoxia-inducible factor.

Biological responses to oxygen availability play important roles in development, physiological homeostasis, and many disease processes. In mammalian cells, this adaptation is mediated in part by a conserved pathway centered on the hypoxia-inducible factor (HIF). HIF is a heterodimeric protein complex composed of two members of the basic helix-loop-helix Per-ARNT-Sim (PAS) (ARNT, aryl hydrocarbon receptor nuclear translocator) domain family of transcriptional activators, HIFalpha and ARNT. Although this complex involves protein-protein interactions mediated by basic helix-loop-helix and PAS domains in both proteins, the role played by the PAS domains is poorly understood. To address this issue, we have studied the structure and interactions of the C-terminal PAS domain of human HIF-2alpha by NMR spectroscopy. We demonstrate that HIF-2alpha PAS-B binds the analogous ARNT domain in vitro, showing that residues involved in this interaction are located on the solvent-exposed side of the HIF-2alpha central beta-sheet. Mutating residues at this surface not only disrupts the interaction between isolated PAS domains in vitro but also interferes with the ability of full-length HIF to respond to hypoxia in living cells. Extending our findings to other PAS domains, we find that this beta-sheet interface is widely used for both intra- and intermolecular interactions, suggesting a basis of specificity and regulation of many types of PAS-containing signaling proteins.

Amino Acid Sequence↗