1ab7

<StructureSection load='1ab7' size='340' side='right'caption='[[1ab7]], [[NMR_Ensembles_of_Models | 30 NMR models]]' scene=''>

<table><tr><td colspan='2'>[[1ab7]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/"bacillus_amyloliquifaciens"_(sic)_fukumoto_1943 "bacillus amyloliquifaciens" (sic) fukumoto 1943]. Full experimental information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1AB7 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1AB7 FirstGlance]. <br>

</td></tr><tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=1ab7 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1ab7 OCA], [https://pdbe.org/1ab7 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1ab7 RCSB], [https://www.ebi.ac.uk/pdbsum/1ab7 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1ab7 ProSAT]</span></td></tr>

[[https://www.uniprot.org/uniprot/BARS_BACAM BARS_BACAM]] Inhibitor of the ribonuclease barnase. Forms a one-to-one non-covalent complex.

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== Publication Abstract from PubMed ==

Barstar an 89-residue protein consisting of four helices and a three-stranded parallel beta-sheet, is the intracellular inhibitor of the endoribonuclease barnase. Barstar C40/82A, a mutant in which the two cysteine residues have been replaced by alanine, has been used as a pseudo wild-type in folding studies and in the crystal structure of the barnase:barstar C40/82A complex. We have determined a high resolution solution structure of barstar C40/82A. The structures of barstar C40/82A and the wild-type are superimposable. A comparison with the crystal structure of the barnase:barstar C40/82A complex revealed subtle differences in the regions involved in the binding of barstar to barnase. Side-chain rotations of residues Asn33, Asp35 and Asp39 and a movement of the binding loop (Pro27-Glu32) towards the binding site of barnase facilitate the formation of interface hydrogen bonds and aromatic contacts in the complex. Extreme line broadening and missing signals in 1H-15N correlation spectra indicate substantial conformational exchange for a large subset of residues. 15N relaxation data at two magnetic field strengths, 11.74 T and 14.10 T, were used to estimate exchange contributions and to map the spectral density function at five frequencies: 0, 50, 60, 450 and 540 MHz. Based on these results, model-free calculations with the inclusion of estimated exchange contributions were used to derive order parameters and internal correlation times. The validity of this approach has been investigated with model-free calculations that incorporate longitudinal relaxation rates and heteronuclear 1H-15N NOE data only at 11.74 T and 14.10 T. The relaxation data suggest substantial conformational exchange in regions of barstar C40/82A, including the binding loop, the second and the third helices, and the second and the third strands. Amide proton exchange experiments suggest a stable hydrogen bond network for all helices and sheets except the third helix and the C-terminal of the second and the third strands. The combined results indicate a rigid body movement of the second helix and twisting motions of the beta-sheet of barstar, which might be important for the interaction with barnase.

NMR 15N relaxation and structural studies reveal slow conformational exchange in barstar C40/82A.,Wong KB, Fersht AR, Freund SM J Mol Biol. 1997 May 2;268(2):494-511. PMID:9159486<ref>PMID:9159486</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

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== References ==

<references/>

[[Category: Fersht, A R]]

[[Category: Freund, S M.V]]

[[Category: Wong, K B]]

[[Category: Ribonuclease inhibitor]]