Structural biology

About: Structural biology is a research topic. Over the lifetime, 2206 publications have been published within this topic receiving 126070 citations.

The Hsp90 molecular chaperone: an open and shut case for treatment

Abstract: The molecular chaperone Hsp90 (90 kDa heat-shock protein) is a remarkably versatile protein involved in the stress response and in normal homoeostatic control mechanisms. It interacts with 'client proteins', including protein kinases, transcription factors and others, and either facilitates their stabilization and activation or directs them for proteasomal degradation. By this means, Hsp90 displays a multifaceted ability to influence signal transduction, chromatin remodelling and epigenetic regulation, development and morphological evolution. Hsp90 operates as a dimer in a conformational cycle driven by ATP binding and hydrolysis at the N-terminus. The cycle is also regulated by a group of co-chaperones and accessory proteins. Here we review the biology of the Hsp90 molecular chaperone, emphasizing recent progress in our understanding of structure-function relationships and the identification of new client proteins. In addition we describe the exciting progress that has been made in the development of Hsp90 inhibitors, which are now showing promise in the clinic for cancer treatment. We also identify the gaps in our current understanding and highlight important topics for future research.

Structure determination of membrane proteins by NMR spectroscopy.

Abstract: Much of postgenomic biochemistry and all of structural biology are based on the premise that the starting point for both understanding specific biochemical processes, such as affinity, reactivity, or transport, and surveying proteomes is determining the three-dimensional structures of proteins. The two well-established methods for structure determination are highly effective when applied to samples of soluble globular proteins and their complexes: witness the enormous growth of the Protein Data Bank.1 However, the vast majority of biological functions are carried out by proteins associated with supramolecular assemblies, whose samples are problematic for both X-ray crystallography and solution NMR spectroscopy, since they are generally difficult to crystallize and do not reorient rapidly even when soluble. The examples of proteins in supramolecular assemblies whose structures have been determined with atomic resolution are exceptional and highlight the importance of developing new methods of experimental protein structure determination. The essential goals of modern structural biology are to have the capability to select proteins for study based on their biological functions and to perform genuinely unbiased surveys of proteomes unfettered by considerations of the solubility, aggregation state, or other physical properties of the polypeptides. NMR spectroscopy has the potential to accomplish these goals, since it can be applied to molecules in all physical states, including the liquid crystalline environments provided by the lipids associated with membrane proteins. Determining the atomic resolution structures of membrane proteins is of particular interest in contemporary structural biology.2 Helical membrane proteins constitute one-third of the expressed proteins encoded in a genome.3,4 Furthermore, many drugs have membrane-bound proteins as their receptors, and mutations in membrane proteins result in human diseases. They also provide daunting technical challenges for all methods of protein structure determination, including NMR spectroscopy.5

Molecular chaperones--cellular machines for protein folding.

Abstract: Proteins are linear polymers synthesized by ribosomes from activated amino acids. The product of this biosynthetic process is a polypeptide chain, which has to adopt the unique three-dimensional structure required for its function in the cell. In 1972, Christian Anfinsen was awarded the Nobel Prize for Chemistry for showing that this folding process is autonomous in that it does not require any additional factors or input of energy. Based on in vitro experiments with purified proteins, it was suggested that the correct three-dimensional structure can form spontaneously in vivo once the newly synthesized protein leaves the ribosome. Furthermore, proteins were assumed to maintain their native conformation until they were degraded by specific enzymes. In the last decade this view of cellular protein folding has changed considerably. It has become clear that a complicated and sophisticated machinery of proteins exists which assists protein folding and allows the functional state of proteins to be maintained under conditions in which they would normally unfold and aggregate. These proteins are collectively called molecular chaperones, because, like their human counterparts, they prevent unwanted interactions between their immature clients. In this review, we discuss the principal features of this peculiar class of proteins, their structure ± function relationships, and the underlying molecular mechanisms.

Assembly reflects evolution of protein complexes

Abstract: A homomer is formed by self-interacting copies of a protein unit. This is functionally important, as in allostery, and structurally crucial because mis-assembly of homomers is implicated in disease. Homomers are widespread, with 50-70% of proteins with a known quaternary state assembling into such structures. Despite their prevalence, their role in the evolution of cellular machinery and the potential for their use in the design of new molecular machines, little is known about the mechanisms that drive formation of homomers at the level of evolution and assembly in the cell. Here we present an analysis of over 5,000 unique atomic structures and show that the quaternary structure of homomers is conserved in over 70% of protein pairs sharing as little as 30% sequence identity. Where quaternary structure is not conserved among the members of a protein family, a detailed investigation revealed well-defined evolutionary pathways by which proteins transit between different quaternary structure types. Furthermore, we show by perturbing subunit interfaces within complexes and by mass spectrometry analysis, that the (dis)assembly pathway mimics the evolutionary pathway. These data represent a molecular analogy to Haeckel's evolutionary paradigm of embryonic development, where an intermediate in the assembly of a complex represents a form that appeared in its own evolutionary history. Our model of self-assembly allows reliable prediction of evolution and assembly of a complex solely from its crystal structure.