192l

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(New page: 200px<br /><applet load="192l" size="450" color="white" frame="true" align="right" spinBox="true" caption="192l, resolution 1.90&Aring;" /> '''A HELIX INITIATION S...)
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[[Image:192l.gif|left|200px]]<br /><applet load="192l" size="450" color="white" frame="true" align="right" spinBox="true"
 
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caption="192l, resolution 1.90&Aring;" />
 
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'''A HELIX INITIATION SIGNAL IN T4 LYSOZYME IDENTIFIED BY POLYALANINE MUTAGENESIS'''<br />
 
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==Overview==
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==A HELIX INITIATION SIGNAL IN T4 LYSOZYME IDENTIFIED BY POLYALANINE MUTAGENESIS==
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To better understand the relation between sequence and structure, and in, an attempt to simplify the protein folding problem, a series of alanine, substitutions was introduced into bacteriophage T4 lysozyme. In contrast, to previous studies in this system, which were restricted to single, alpha-helices, the present analysis included a helix-turn-helix region, a, loop-helix region, and two alpha-helices that were well separated in the, three-dimensional structure. It was shown previously that T4 lysozyme is, very tolerant of alanine substitutions within alpha-helices, especially at, solvent-exposed sites. The present study shows that the protein is also, tolerant of such substitutions in turn and loop regions, although less, than in helices. The results confirm that the structural information in, the amino acid sequence is highly redundant. For example, the protein with, the sequence 127AAAAAALAAAAWAAA141 folds normally, has melting temperature, only 0.8 degrees C lower than wildtype, and has a crystal structure that, is also very similar to wildtype. Polyalanine substitutions within turns, or loops can, however, lead to differences in structure and in folding. In, one example the triple substitution K35A/S36A/P37A caused this region of, the molecule to change to a more helical conformation. In a second case, the mutant with the sequence 34AAAAALAAAKAALAAA49, which spans a, loop-helix region, had a dramatically altered thermal unfolding, transition, suggesting that this region may tend to form a single, uninterrupted, helix. Substitution of Ala38 in the above construct with, aspartic acid caused the unfolding to be more like wildtype, suggesting, that residue 38, which is at a helix-capping position in the wildtype, structure, provides an initiation signal that is essential in the, polyalanine mutant for the correct formation of alpha-helix 39-50. In a, typical protein, the information that codes for the 3D structure is, presumably distributed over many amino acids. The present results suggest, that in simplified sequences the key folding information may be restricted, to a subset of critical residues, and so be more readily accessible to, experimental analysis.
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<StructureSection load='192l' size='340' side='right'caption='[[192l]], [[Resolution|resolution]] 1.90&Aring;' scene=''>
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== Structural highlights ==
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<table><tr><td colspan='2'>[[192l]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Escherichia_virus_T4 Escherichia virus T4]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=192L OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=192L FirstGlance]. <br>
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</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 1.9&#8491;</td></tr>
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<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CL:CHLORIDE+ION'>CL</scene>, <scene name='pdbligand=HED:2-HYDROXYETHYL+DISULFIDE'>HED</scene></td></tr>
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<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=192l FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=192l OCA], [https://pdbe.org/192l PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=192l RCSB], [https://www.ebi.ac.uk/pdbsum/192l PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=192l ProSAT]</span></td></tr>
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</table>
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== Function ==
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[https://www.uniprot.org/uniprot/ENLYS_BPT4 ENLYS_BPT4] Endolysin with lysozyme activity that degrades host peptidoglycans and participates with the holin and spanin proteins in the sequential events which lead to the programmed host cell lysis releasing the mature viral particles. Once the holin has permeabilized the host cell membrane, the endolysin can reach the periplasm and break down the peptidoglycan layer.<ref>PMID:22389108</ref>
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== Evolutionary Conservation ==
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[[Image:Consurf_key_small.gif|200px|right]]
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Check<jmol>
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<jmolCheckbox>
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<scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/92/192l_consurf.spt"</scriptWhenChecked>
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<scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview01.spt</scriptWhenUnchecked>
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<text>to colour the structure by Evolutionary Conservation</text>
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</jmolCheckbox>
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</jmol>, as determined by [http://consurfdb.tau.ac.il/ ConSurfDB]. You may read the [[Conservation%2C_Evolutionary|explanation]] of the method and the full data available from [http://bental.tau.ac.il/new_ConSurfDB/main_output.php?pdb_ID=192l ConSurf].
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<div style="clear:both"></div>
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==About this Structure==
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==See Also==
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192L is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Bacteriophage_t4 Bacteriophage t4] with CL and HED as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Lysozyme Lysozyme], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.17 3.2.1.17] Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=192L OCA].
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*[[Lysozyme 3D structures|Lysozyme 3D structures]]
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== References ==
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==Reference==
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<references/>
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A helix initiation signal in T4 lysozyme identified by polyalanine mutagenesis., Zhang XJ, Baase WA, Matthews BW, Biophys Chem. 2002 Dec 10;101-102:43-56. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=12487988 12487988]
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__TOC__
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[[Category: Bacteriophage t4]]
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</StructureSection>
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[[Category: Lysozyme]]
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[[Category: Escherichia virus T4]]
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[[Category: Single protein]]
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[[Category: Large Structures]]
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[[Category: Matthews, B.W.]]
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[[Category: Matthews BW]]
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[[Category: Zhang, X.J.]]
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[[Category: Zhang X-J]]
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[[Category: CL]]
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[[Category: HED]]
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[[Category: hydrolase (o-glycosyl)]]
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''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Tue Nov 20 10:30:56 2007''
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Current revision

A HELIX INITIATION SIGNAL IN T4 LYSOZYME IDENTIFIED BY POLYALANINE MUTAGENESIS

PDB ID 192l

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