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Journal Issue - Volume 5 Issue 8 (August 1996)

Abstract There have been few studies of protein folding in the endoplasmic reticulum of intact mammalian cells. In the one case where the in vivo and in vitro folding pathways of a mammalian secretory protein have been compared, the folding of the human chorionic gonadotropin β subunit (hCG‐β), the order of formation of the detected folding intermediates is the same. The rate and efficiency with which multidomain proteins such as...

Abstract Equine infectious anemia virus (EIAV), the causative agent of infectious anemia in horses, is a member of the lentiviral family. The virus‐encoded proteinase (PR) processes viral polyproteins into functional molecules during replication and it also cleaves viral nucleocapsid protein during infection. The X‐ray structure of a complex of the I54G mutant of EIAV PR with the inhibitor HBY‐793 was solved at 1.8 Å resolution and...

Abstract The binding interactions of N‐acetyl‐D‐neuraminic acid and N,N' diacetyl‐chitobiose (GlcNAc‐β‐1,4‐GIcNAc), observed in crystal complexes of wheat germ agglutinin (WGA) at four independent sites/monomer, were analyzed and compared with the modeling program HINT (Hydropathic INTeractions). This empirical method allows assessment of relative ligand binding strength and is particularly applicable to cases of weak binding where...

Abstract The role of charges near the pore mouth has been discussed in theoretical work about ion channels. To introduce new negative charges in a channel protein, amino groups of porin from Rhodobacter capsulatus 37b4 were succinylated with succinic anhydride, and the precise extent and sites of succinylations and structures of the succinyl‐porins determined by mass spectrometry and X‐ray crystallography. Molecular weight and peptide mapping...

Abstract Lectins form a class of proteins that have evolved a specialized carbohydrate‐binding function. Based on amino acid sequence analysis, several lectin families have been described and a lectin domain, the (QxW)3 domain, was discussed recently based on 11 family members. In this paper, the (QxW)3 domain family is extended to 45 sequences, several of which have very low sequence identity with the previously known members of the family. A...

Abstract The structure of a symmetric T3Rf3 insulin hexamer, complexed with 4‐hydroxybenzamide, has been determined using X‐ray crystallographic techniques. Data were measured from six crystals grown in microgravity to a resolution of 1.4 Å and the structure has been refined including the contributions from hydrogen atoms. The crystals are isomorphous with T3Rf3 complexes of phenolic derivatives as well as with uncomplexed forms. Unlike the...

Abstract The NMR solution structure of the pheromone Er‐11, a 39‐residue protein from the ciliated protozoan Euplotes raikovi, was calculated with the distance geometry program DIANA from 449 NOE upper distance constraints and 97 dihedral angle constraints, and the program OPAL was employed for structure refinement by molecular mechanics energy minimization in a water bath. For a group of 20 conformers used to characterize the solution...

Abstract The function of the conserved Phe 100 residue of RNase T1 (EC 3.1.27.3) has been investigated by site‐directed mutagenesis and X‐ray crystallography. Replacement of Phe 100 by alanine results in a mutant enzyme with kcat reduced 75‐fold and a small increase in Km for the dinucleoside phosphate substrate GpC. The Phe 100 Ala substitution has similar effects on the turnover rates of GpC and its minimal analogue GpOMe, in which the...

Abstract Factor VIIa (fVIIa) is composed of four discrete domains, a 7‐carboxyglutamic acid (Gla)‐containing domain, two epidermal growth factor (EGF)‐like domains, and a serine protease domain, all of which appear to be involved, to different extents, in an optimal interaction with tissue factor (TF). All except the second EGF‐like domain contain at least one Ca2+ binding site and many properties of fVIIa, e.g., TF and phospholipid binding and...

Abstract The active site of pig kidney fructose‐l,6‐bisphosphatase (EC 3.1.3.11) is shared between subunits, Arg‐243 of one chain interacting with fructose‐1,6‐bisphosphate or fructose‐2,6‐bisphosphate in the active site of an adjacent chain. In this study, we present the X‐ray structures of the mutant version of the enzyme with Arg‐243 replaced by alanine, crystallized in both T and R allosteric states. Kinetic characteristics of...

Abstract The unfolding of recombinant human β‐NGF (NGF) in guanidine hydrochloride (GdnHCl) was found to be time dependent with the denaturation midpoint moving to lower GdnHCl concentration over time. Dissociation and extensive unfolding of the NGF dimer occurred rapidly in 5 M GdnHCl, but further unfolding of the molecule occurred over many days at 25 °C. Fluorescence spectroscopy, size‐exclusion and reversed‐phase HPLC,...

Abstract RNA binding domains (RBDs) are members of a large family of proteins that share minimal sequence conservation but adopt an αβ sandwich global fold. Defining the contributions of specific amino acids to RBD structure and RNA binding is critical to understanding the functions of these proteins. In these experiments with the human U1A N‐terminal RNA binding domain (RBD1), the contributions from each of its four tyrosines to...

Abstract Here we describe how the systematic redesign of a protein's hydrophobic core alters its structure and stability. We have repacked the hydrophobic core of the four‐helix‐bundle protein, Rop, with altered packing patterns and various side chain shapes and sizes. Several designs reproduce the structure and native‐like properties of the wild‐type, while increasing the thermal stability. Other designs, either with similar sizes...

Abstract Because regions on the messenger ribonucleic acid differ in the rate at which they are translated by the ribosome and because proteins can fold cotranslationally on the ribosome, a question arises as to whether the kinetics of translation influence the folding events in the growing nascent polypeptide chain. Translationally slow regions were identified on mRNAs for a set of 37 multidomain proteins from Escherichia coli with...

Abstract IclR protein, the repressor of the aceBAK operon of Escherichia coli, has been examined by time‐of‐flight mass spectrometry, with ionization by matrix assisted laser desorption or by electrospray. The purified protein was found to have a smaller mass than that predicted from the base sequence of the cloned icl R gene. Additional measurements were made on mixtures of peptides derived from IclR by treatment with trypsin and cyanogen ...

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