Search results for "structural biology"

Novel structural insights into F-actin-binding and novel functions of calponin homology domains.

2008

Tandem calponin homology (CH) domains are well-known actin filaments (F-actin) binding motifs. There has been a continuous debate about the details of CH domain-actin interaction, mainly because atomic level structures of F-actin are not available. A recent electron microscopy study has considerably advanced our structural understanding of CH domain:F-actin complex. On the contrary, it has recently also been shown that CH domains can bind other macromolecular systems: two CH domains from separate polypeptides Ncd80, Nuf2 can form a microtubule-binding site, as well as tandem CH domains in the EB1 dimer, while the single C-terminal CH domain of alpha-parvin has been observed to bind to a alp…

Evolutionary history and diversity of arthropod hemocyanins

2004

Hemocyanins are copper-containing, multi-subunit proteins that transport oxygen in the hemolymph of many molluscs and arthropods [Markl and Decher, Adv. Comp. Environ. Physiol. 13 (1992) 325; van Holde et al., J. Biol. Chem. 276 (2001) 15563]. Arthropod hemocyanins originated more than 550 million years ago from oxygen-consuming phenoloxidases. Hemocyanins are present in various Onychophora, Chelicerata, Myriapoda, Crustacea, and Hexapoda, but subunit evolution differs striking in these arthropod subphyla. Hemocyanins also gave rise to non-respiratory proteins (crustacean pseudo-hemocyanins, insect hexamerins, and hexamerin receptors), which most likely have storage functions.

Solubilization of an oligomycin-sensitive ATPase complex fromRhodospirillum rubrumchromatophores and its inhibition by various antibiotics

1978

Immunoelectron Microscopy of Hemocyanin from the Keyhole Limpet (Megathura crenulata): A Parallel Subunit Model

1993

Abstract Immunoelectron microscopy has been performed using negatively stained immune complexes of keyhole limpet hemocyanin (KLH) subunit 2 di- and multidecamers with domain-specific monoclonal antibodies. One antibody (KLH2 a macr 1) links the hemocyanin molecules in a side-to-side pattern, whereas the other antibody (KLH2 fg macr 1) links the molecules end-to-end. From existing knowledge of the domain sequence of KLH subunit 2, these data provide support for a parallel arrangement of subunits within each decamer. Ten N-terminal a macr: domains are then present at the noncollar region of each decamer with 10 C-terminal g macr domains at the collar region. The immunonegative staining data …

Bringing a Molecular Plus One: Synergistic Binding Creates Guest-Mediated Three-Component Complexes

2020

Cethyl-2-methylresorcinarene (A), pyridine (B), and a set of 10 carboxylic acids (Cn) associate to form A·B·Cn ternary assemblies with 1:1:1 stoichiometry, representing a useful class of ternary systems where the guest mediates complex formation between the host and a third component. Although individually weak in solution, the combined strength of the multiple noncovalent interactions organizes the complexes even in a highly hydrogen-bond competing methanol solution, as explored by both experimental and computational methods. The interactions between A·B and Cn are dependent on the pKa values of carboxylic acids. The weak interactions between A and C further reinforce the interactions betw…

Application of the negative staining technique to both aqueous and organic solvent solutions of polymer particles

1999

Abstract Transmission electron microscopy (TEM) imaging of several different polymers in aqueous and organic solutions using the negative staining technique is demonstrated, to emphasise the possibilities of this specimen preparation technique for polymer science. Negative stains can readily be prepared in both water and organic solvents (e.g. dimethyl formamide (DMF), dimethyl sulfoxide (DMSO) and tetrahydrofurane (THF)). Polymer particle size, size distribution and shape seen in negative stain correlates well with those of unstained materials. The particle surface and smaller particles (e.g. 10–20 nm) are more clearly defined in the presence of a negative stain. The inherent problems of s…

The NreA Protein Functions as a Nitrate Receptor in the Staphylococcal Nitrate Regulation System

2013

Staphylococci are able to use nitrate as an alternative electron acceptor during anaerobic respiration. The regulation of energy metabolism is dependent on the presence of oxygen and nitrate. Under anaerobic conditions, staphylococci employ the nitrate regulatory element (Nre) for transcriptional activation of genes involved in reduction and transport of nitrate and nitrite. Of the three proteins that constitute the Nre system, NreB has been characterized as an oxygen sensor kinase and NreC has been characterized as its cognate response regulator. Here, we present structural and functional data that establish NreA as a new type of nitrate receptor. The structure of NreA with bound nitrate w…

The role of pH on instability and aggregation of sickle hemoglobin solutions

2004

Understanding the physical basis of protein aggregation covers strong physical and biomedical interests. Sickle hemoglobin (HbS) is a point-mutant form of normal human adult hemoglobin (HbA). It is responsible for the first identified "molecular disease," as its propensity to aggregation is responsible for sickle cell disease. At moderately higher than physiological pH value, this propensity is inhibited: The rate of aggregate nucleation becomes exceedingly small and solubility after polymerization increases. These order-of-magnitude effects on polymer nucleation rates and concurrent relatively modest changes of solubility after polymerization are here shown to be related to both pH-induced…

Keyhole Limpet Hemocyanin (KLH): Slow In Vitro Reassociation of KLH1 and KLH2 from Immucothel®

1998

Abstract Following our in vitro reassociation of keyhole limpet hemocyanin subunits in the presence of high concentrations (100 mM each) of calcium and magnesium chloride (Harris et al., 1997a, Micron 28, 31–41; 1997b, Micron 28, 43–56), we have now extended our investigations by using a buffer system containing a lower concentration of the two divalent cations (10 mM each). Reassociation of mixed KLH subunits present in the commercially available product Immucothel® was performed using a standardized buffer solution containing 50 mM Tris–HCl, 150 mM NaCl, 10 mM CaCl2 and 10 mM MgCl2 (pH 7.4) over a minimum period of one week, at 4°C. This solution was selected as being close to our KLH sta…

Human neuroglobin: crystals and preliminary X-ray diffraction analysis

2002

Neuroglobin, a recently discovered member of the haemoglobin superfamily, is primarily expressed in the brain of humans and other vertebrates, where it has been proposed to enhance O(2) supply in response to hypoxia or ischaemia, protecting the neuron from hypoxic injury. Neuroglobin is the first example of a vertebrate haemoglobin in which a hexacoordinate haem geometry has been detected. A triple mutant (replacing three Cys residues) of human neuroglobin (151 amino acids) has been expressed in Escherichia coli, purified and crystallized in two crystal forms, the best of which diffracts to 1.95 A resolution using synchrotron radiation. The crystals belong to space group P2(1), with unit-ce…