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B Chain (b + chain)

Distribution by Scientific Domains

Chemistry	77%

Selected Abstracts

Genetic organization of A chain and B chain of ,-bungarotoxin from Taiwan banded krait (Bungarus multicinctus)

FEBS JOURNAL, Issue 15 2000
A chain genes, B chain genes do not share a common origin
,-Bungarotoxin, the main presynaptic neurotoxin purified from the venom of Bungarus multicinctus, consists of two dissimilar polypeptide chains, the A chain and the B chain, cross-linked by an interchain disulfide bond. In this study, A and B chain genes isolated from the liver of B. multicinctus encoded the A and B chain precursors, respectively. Analyses of the coding regions of the A and B chain genes revealed that both consist of three exons and two introns. The sequences of all exon/intron junctions agree with the GT/AG rule. However, sequence alignment and phylogenetic analysis did not support that the evolution of A and B chain genes are closely related. Comparative analysis of A chain genes with Viperinae and Crotalinae phospholipase A2 genes indicated that genetic divergence of the A chain and phospholipase A2s was in accordance with their family. Moreover, evolutionary divergence of the intron and exon regions of the A chain, as observed for phospholipase A2 genes, was not consistent. Noticeably, the transcription of A and B chain genes may be regulated under different transcription factors as revealed by analyses of their promoter sequences. In terms of the finding that A and B chains are encoded separately by different genes, this strongly supports the view that the intact ,-bungarotoxin molecules should be derived from the pairing of A and B chains after their mRNAs are translated. [source]

Binding sites of [Ru(bpy)2(H2O)2](BF4)2 with sulfur- and histidine-containing peptides studied by electrospray ionization mass spectrometry and tandem mass spectrometry

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 1 2005
Jin Hong
Abstract The composition and binding sites of cis -[Ru(II)(bpy)2]2+ -bound sulfur-containing peptides of Met-Arg-Phe-Ala, glutathione and oxidized glutathione, and also histidine-containing peptide of oxidized insulin B chain, were investigated by electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS). The composition of Ru(II)-containing peptides was precisely determined by ESI-MS, zoom scan and simulation of isotope distribution patterns. MS/MS analysis shows that, in sulfur-containing peptides, the Ru(II) complex prefers to anchor to a carboxyl group, although some other potential binding sites of thiol, thioether and N-terminal amino groups present in these peptides, and in oxidized insulin B chain, Ru(II) first anchors to His10, then either to the hydroxyl group of Thr27 or to the carboxyl group of Ala30. Its secondary structure and microenvironment surrounding the potential binding sites may affect the binding ability of cis -[Ru(II)(bpy)2]2+ to oxidized insulin B chain. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Sugar-complex structures of the C-half domain of the galactose-binding lectin EW29 from the earthworm Lumbricus terrestris

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 1 2009
Ryuichiro Suzuki
R-type lectins are one of the most prominent types of lectin; they exist ubiquitously in nature and mainly bind to the galactose unit of sugar chains. The galactose-binding lectin EW29 from the earthworm Lumbricus terrestris belongs to the R-type lectin family as represented by the plant lectin ricin. It shows haemagglutination activity and is composed of a single peptide chain that includes two homologous domains: N-terminal and C-terminal domains. A truncated mutant of EW29 comprising the C-terminal domain (rC-half) has haemagglutination activity by itself. In order to clarify how rC-half recognizes ligands and shows haemagglutination activity, X-ray crystal structures of rC-half in complex with d -lactose and N -acetyl- d -galactosamine have been determined. The structure of rC-half is similar to that of the ricin B chain and consists of a ,-trefoil fold; the fold is further divided into three similar subdomains referred to as subdomains ,, , and ,, which are gathered around the pseudo-threefold axis. The structures of sugar complexes demonstrated that subdomains , and , of rC-half bind terminal galactosyl and N -acetylgalactosaminyl glycans. The sugar-binding properties are common to both ligands in both subdomains and are quite similar to those of ricin B chain,lactose complexes. These results indicate that the C-terminal domain of EW29 uses these two galactose-binding sites for its function as a single-domain-type haemagglutinin. [source]

Comparison of the Embryotoxic Effects of Saporin, Agrostin (Type 1 Ribosome-Inactivating Proteins) and Ricin (a Type 2 Ribosome-Inactivating Protein

BASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 6 2001
Wood-Yee Chan
Saporin and agrostin had similar embryotoxicity which was approximately 105 times weaker than that of ricin and its A and B chains, and the embryotoxicity of saporin and agrostin increased gradually with the dosage. In contrast, there was an abrupt rise in embryotoxictiy of ricin-A chain and B chain as the dose was raised from 10 to 20 ng ml,1. Saporin and agrostin did not affect the heart-beat and otic placode, but at 10 ng ml,1 ricin and 40 ng ml,1 ricin-A chain and B chain, all of the treated embryos exhibited abnormalities in heart-beat, yolk sac circulation, body axis, optic placode, otic placode, forelimb buds, branchial apparatus and cranial neural tube. [source]

Primary Steps of pH-Dependent Insulin Aggregation Kinetics are Governed by Conformational Flexibility

CHEMBIOCHEM, Issue 11 2009
Jürgen Haas Dr.
Abstract Insulin aggregation critically depends on pH. The underlying energetic and structural determinants are, however, unknown. Here, we measure the kinetics of the primary aggregation steps of the insulin monomer in vitro and relate it to its conformational flexibility. To assess these primary steps the monomer concentration was monitored by mass spectrometry at various pH values and aggregation products were imaged by atomic force microscopy. Lowering the pH from 3 to 1.6 markedly accelerated the observed aggregation kinetics. The influence of pH on the monomer structure and dynamics in solution was studied by molecular dynamics simulations, with the protonation states of the titrable groups obtained from electrostatic calculations. Reduced flexibility was observed for low pH values, mainly in the C terminus and in the helix of the B chain; these corresponded to an estimated entropy loss of 150 J,mol,1,K,1. The striking correlation between entropy loss and pH value is consistent with the observed kinetic traces. In analogy to the well-known , value analysis, this result allows the extraction of structural information about the rate determining transition state of the primary aggregation steps. In particular, we suggest that the residues in the helix of the B chain are involved in this transition state. [source]

Genetic organization of A chain and B chain of ,-bungarotoxin from Taiwan banded krait (Bungarus multicinctus)

A neutron crystallographic analysis of T6 porcine insulin at 2.1,Å resolution

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 10 2009
Wakari Iwai
Neutron diffraction data for T6 porcine insulin were collected to 2.1,Å resolution from a single crystal partly deuterated by exchange of mother liquor. A maximum-likelihood structure refinement was undertaken using the neutron data and the structure was refined to a residual of 0.179. The hydrogen-bonding network of the central core of the hexamer was observed and the charge balance between positively charged Zn ions and their surrounding structure was interpreted by considering the protonation and/or deprotonation states and interactions of HisB10, water and GluB13. The observed double conformation of GluB13 was essential to interpreting the charge balance and could be compared with the structure of a dried crystal of T6 human insulin at 100,K. Differences in the dynamic behaviour of the water molecules coordinating the upper and lower Zn ions were observed and interpreted. The hydrogen bonds in the insulin molecules, as well as those involving HisB10 and GluB13, are discussed. The hydrogen/deuterium (H/D) exchange ratios of the amide H atoms of T6 porcine insulin in crystals were obtained and showed that regions highly protected from H/D exchange are concentrated in the centre of a helical region of the B chains. From the viewpoint of soaking time versus H/D-exchange ratios, the amide H atoms can be classified into three categories. [source]