摘要:

AbstractThe model structure previously proposed for human C5a, based upon the crystal structure of the homologous protein human C3a, is compared to the solution structure of human C5a recently determined by nuclear magnetic resonance (NMR) methods in our laboratory. The general folding and helix topography of the C5a protein were modeled very well. The N‐terminus, which is disordered in teh C3a crystal, was correctly predicted in the C5a model both as to its being a helix and as to its docking site on the rest of the molecule. On the other hand, the NMR data show that the biologically important C‐terminal residues are disordered in solution, unlike the model and the C3a crystal structure where this region was heli

ISSN:0887-3585    

DOI:10.1002/prot.340030302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractPseudomonas aeruginosaexotoxin A is representative of a class of enzymes, the monoADP‐ribosyl, which catalyze the covalent transfer of an ADP‐ribose moiety of NAD+to a target substrate. Availability of the three‐dimensional structure of exotoxin A provides the opportunity for mapping substrate binding sites and suggesting which amino acid residues may be involved in catalysis. Data from several sources have been combined to develop a proposal for the NAD+binding site of exotoxin A: the binding of NAD+fragments adenosine, AMP, and ADP have been delineated crystallographically to 6.0, 6.0, and 2.7 Å, respectively; significant sequence homology spanning 60 residues has been found between exotoxin A and diphtheria toxin, which has the identical enzymatic activity; iodination of exotoxin A, under conditions in which only tyrosine 481 is iodinated in the enzymatic domain, abolishes ADP‐ribosyl transferase

ISSN:0887-3585    

DOI:10.1002/prot.340030303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractAn antigen‐binding fragment (Fab) from a murine monoclonal antibody (4‐4‐20) with high affinity for fluorescein was cocrystallized with ligand in polyethylene glycol (PEG) and 2‐methl‐2,4‐pentanediol (MPD) in forms suitable for X‐ray analyses. In MPD the affinity of the intact antibody for fluorescein was 300 times lower than the value (3.4 × 1010M−1) obtained in aqueous buffers. This decreased affinity was manifested by the partial release of bound fluorescein when MPD was added to solutions of liganded Feb during crystallization trials, In PEG, the ligand remained firmly bound to the protein. The liganded Feb crystallized in the monoclinic space groupP21in PEG, witha= 58.6,b= 97.2,c= 44.5 Å and β = 95.2°. In MPD the space group was triclinicP1, witha= 58.3,b= 43.4,c= 42.3 Å, α = 83.9°, β = 87.6°, and γ = 84.5°. X‐ray diffraction data were collected for both forms to 2.5‐Å resolution. Surprisingly, the triclinic form of the liganed antifluorescyl Feb had the same space group, closely similar cell dimensions, and practically the same orientation in the unit cell as an unliganded Fab (BV04‐01) with act

ISSN:0887-3585    

DOI:10.1002/prot.340030304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractThree epitopes have been localized by immunoelectron microscopy on subunitsAa6of the 4 × 6‐meric hemocyanin of the scorpionAndroctonus australis. Soluble immunocomplexes composed of monoclonal antibodies and of native hemocyanin were purified, negatively stained with uranyle acetate by the single‐layer technique, and examined under the electron microscope (EM). The molecule images were digitized, aligned, and submitted to correspondence analysis according to the method of Van Heel and Frank (Ultramicroscopy6: 187‐194, 1981). A high‐precision localization of the attachment point of the Fab arm to the antigen was achieved through a careful analysis of the average images. This method easily allowed the discrimination of epitopes located in different domains (Mr 20 kDa) of the same subunit. Nonoverlapping epitopes located in the same structural domain of subunit Aa6 could be distinguished by the stain exclusion patterns of their Fab arms. The method is general and may be used for epitope mapping in any antigen producing definite

ISSN:0887-3585    

DOI:10.1002/prot.340030305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractA newly discovered iron‐containing protein, isolated from the bacteriumDesulfovibrio vulgaris(Hildenborough, NCIB 8303), has been crystallized. The molecule appears to be a dimer of mass 44kDa. This protein has iron centers with spectroscopic similarities to those in rubredoxins and in hemerythrins.The X‐ray diffraction shows symmetry consistent with space group I222 or I212121. Cell parameters are a = 49.2 Å, b = 81.3 Å, c= 100.1 Å, and α, β, γ = 90°. X‐ray diffraction data have been collected to 3.0 Å, and a search for useful heavy atom derivatives is in progress for the analysis of the crystal structure of th

ISSN:0887-3585    

DOI:10.1002/prot.340030306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractThe amphipathic helical theory of Segrest and colleagues (FEBS Lett.: 38: 247–253, 1974) proposes that the lipid‐binding segments of serum apolipoproteins are in an alpha helical conformation. Furthermore the helices have a hydrophobic face and a hydrophilic face with a specific distribution of positively and negatively charged residues. The importance of the pattern of the charged residues in the lipid binding and lecithin:cholesterol acyltransferase (LCAT) activation by the segments is still debated. We designed a 30‐residue peptide, GALA, which in the alpha helical conformation hs a hydrophilic face composed of glutamic acid residues (Sabbarao et al.:Biochemistry26: 2964–2972, 1987). GALA behaves like the serum apolipoproteins in its interaction with dimyristoylphospatidylcholine (DMPC) at neutral pH; the amino terminal tryptophan of GALA undergoes a blue shift in its fluorescence emission spectrum, and the circular dichroism (CD) spectrum indicates that GALA acquires alpha helical structure in the presence of DMPC. A DMPC‐GALA:19/1 (molar ratio) complex can be isolated by gel‐permeation chromatography. This complex has a discoidal structure with the approximate dimensions of 44‐Å diameter. GALA edge thickness and a 170‐ to 350‐Å diameter. GALA activates LCAT with DMPC but not with unsaturated phospholipids as the substrate. The apparent partition coefficient of GALA into DMPC vesicles is 100‐fold larger than into egg phosphatidlylcholine vesicles. The interaction of GALA with unsaturated lipids at neutral pH is so weak that no detectable change in the spectroscopic properties of GALA or the structure of the liposomes can be detected under the conditions used here. The sequence of GALA differs from previously studied model Apo A1 peptides by the absence of positively charged residues on the hydrophilic face. This indicates that positive charges in Apo A1‐like peptides are not required in order to form discoidal structures with saturated phospholipids or to activate LCAT wit

ISSN:0887-3585    

DOI:10.1002/prot.340030307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractTo explain the rapidity of the process of protein folding, we cite two aspects of hydrophobic interaction: its long‐range nature and the specificity of pairing after the formation of secondary structures. These two factors, when incorporated with the growth‐type mechanism, can determine the folding pathway of proteins. This mechanism is applied to myoglobin. Appropriate introduction of side chins of amino acid residues and the heme group attached to His 93 yield a refolded tertiary structure that is in good agreement with the native struct

ISSN:0887-3585    

DOI:10.1002/prot.340030308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

ISSN:0887-3585    

DOI:10.1002/prot.340030301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY