Structural heterogeneity of the binding sites of HSA for phenyl‐groups and medium‐chain fatty acids

Lund, Martin; Bjerrum, Ole J.; Bjerrum, Morten J.

doi:10.1046/j.1432-1327.1999.00175.x

Cited by 5 publications

(2 citation statements)

References 23 publications

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“…As long ago as 1950, Karush proposed that serum albumin's ability to bind to many differently shaped ligands was due to an ensemble of structures in equilibrium and further that each ligand would associate with the best fitting member of the ensemble (77). Experiments up to the present continue to support Karush's interpretation (78). Karush called this type of binding configurational adaptability, although conformational adaptability is probably more appropriate.…”

Section: Discussionmentioning

confidence: 98%

Clusterin, a Binding Protein with a Molten Globule-like Region

et al. 2001

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Clusterin is a heterodimeric glycoprotein found in many tissues of the body and is the most abundant protein secreted by cultured rat Sertoli cells. The function of clusterin is unknown, but it has been associated with cellular injury, lipid transport, apoptosis, and it may be involved in the clearance of cellular debris caused by cell injury or death. Consistent with this last idea, clusterin has been shown to bind to a variety of molecules with high affinity including lipids, peptides, and proteins and the hydrophobic probe 1-anilino-8-naphthalenesulfonate (ANS). Given this variety of ligands, clusterin must have specific structural features that provide the protein with its promiscuous binding activity. Using sequence analyses, we show that clusterin likely contains three long regions of natively disordered or molten globule-like structures containing putative amphipathic alpha-helices. These disordered regions were highly sensitive to trypsin digestion, indicating a flexible nature. The effects of denaturation on the fluorescence of the clusterin-ANS complex were compared between proteins with structured binding pockets and molten globular forms of proteins. Clusterin bound ANS in a manner that was very similar to that of molten globular proteins. Furthermore, we found that, when bound to ANS, at least one cleavage site within the protease-sensitive disordered regions of clusterin was protected from trypsin digestion. In addition, we show that clusterin can function as a biological detergent that can solubilize bacteriorhodopsin. We propose that natively disordered regions with amphipathic helices form a dynamic, molten globule-like binding site and provide clusterin the ability to bind to a variety of molecules.

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Section: Discussionmentioning

confidence: 98%

Clusterin, a Binding Protein with a Molten Globule-like Region

et al. 2001

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“…Studies on albumin binding to the present support Karush's original proposal of an ensemble of structures, but with some added and interesting twists such as the existence of different conformers with slow rates of conversion, corresponding to slightly less than 15 seconds. 20 Amino acid side chains differ from one to another but yet all are joined by the same peptide bond within proteins. This indicates the need for conformational changes during protein synthesis in order to accommodate the differently shaped side chains.…”

Section: Introductionmentioning

confidence: 99%

Intrinsically disordered protein

Dunker

Lawson

Brown

et al. 2001

Journal of Molecular Graphics and Modelling

2,105

2,085

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Proteins can exist in a trinity of structures: the ordered state, the molten globule and the random coil. Five examples follow which suggest that native protein structure can correspond to any of the three states (not just the ordered state) and that protein function can arise from any of the three states and their transitions. 1. In a process that likely mimics infection, fd phage converts from the ordered into the disordered molten globular state. 2. Nucleosome hyperacetylation is crucial to DNA replication and transcription; this chemical modification greatly increases the net negative charge of the nucleosome core particle. We propose that the increased charge imbalance promotes its conversion to a much less rigid form. 3. Clusterin contains an ordered domain and also a native molten globular region. The molten globular domain likely functions as a proteinaceous detergent for cell remodeling and removal of apoptotic debris. 4. In a critical signaling event, a helix in calcineurin becomes bound and surrounded by calmodulin, thereby turning on calcineurin's serine/threonine phosphatase activity.Locating the calcineurin helix within a region of disorder is essential for enabling calmodulin to surround its target upon binding. 5. Calsequestrin regulates calcium levels in the sarcoplasmic reticulum by binding about 50 ions/molecule. Disordered polyanion tails at the carboxy terminus bind many of these calcium ions, perhaps without adopting a unique structure. In addition to these examples, 16 more proteins with native disorder will be discussed. These disordered regions include molecular recognition domains, protein folding inhibitors, flexible linkers, entropic springs, entropic clocks and entropic bristles.Motivated by such examples of intrinsic disorder, we are studying the relationships between amino acid sequence and order/disorder, and from this information we are predicting intrinsic order/disorder from amino acid sequence.The sequence/structure relationships indicate that disorder is an encoded property, and the predictions strongly suggest that proteins in nature are much richer in intrinsic disorder than are those in the Protein Data Bank. Recent predictions on 29 genomes indicate that proteins from eucaryotes apparently have more intrinsic disorder than those from either bacteria or archaea, with typically > 30 % of eucaryotic proteins having disordered regions of length = 50 consecutive residues.

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Conformational Transitions of the Three Recombinant Domains of Human Serum Albumin Depending on pH

Dockal¹,

Carter²,

Rüker³

2000

Journal of Biological Chemistry

425

323

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Human serum albumin (HSA) is a protein of 66.5 kDa that is composed of three homologous domains, each of which displays specific structural and functional characteristics. HSA is known to undergo different pH-dependent structural transitions, the N-F and F-E transitions in the acid pH region and the N-B transition at slightly alkaline pH. In order to elucidate the structural behavior of the recombinant HSA domains as standalone proteins and to investigate the molecular and structural origins of the pH-induced conformational changes of the intact molecule, we have employed fluorescence and circular dichroic methods. Here we provide evidence that the loosening of the HSA structure in the N-F transition takes place primarily in HSA-DOM III and that HSA-DOM I undergoes a structural rearrangement with only minor changes in secondary structure, whereas HSA-DOM II transforms to a molten globulelike state as the pH is reduced. In the pH region of the N-B transition of HSA, HSA-DOM I and HSA-DOM II experience a tertiary structural isomerization, whereas with HSA-DOM III no alterations in tertiary structure are observed, as judged from near-UV CD and fluorescence measurements.

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Structural heterogeneity of the binding sites of HSA for phenyl‐groups and medium‐chain fatty acids

Cited by 5 publications

References 23 publications

Clusterin, a Binding Protein with a Molten Globule-like Region

Clusterin, a Binding Protein with a Molten Globule-like Region

Intrinsically disordered protein

Conformational Transitions of the Three Recombinant Domains of Human Serum Albumin Depending on pH

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