View source for 1fmh


==NMR SOLUTION STRUCTURE OF A DESIGNED HETERODIMERIC LEUCINE ZIPPER==
<StructureSection load='1fmh' size='340' side='right'caption='[[1fmh]]' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1fmh]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Saccharomyces_cerevisiae_S288C Saccharomyces cerevisiae S288C]. Full experimental information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1FMH OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1FMH FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">Solution NMR, 25 models</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=ACE:ACETYL+GROUP'>ACE</scene>, <scene name='pdbligand=NH2:AMINO+GROUP'>NH2</scene></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=1fmh FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1fmh OCA], [https://pdbe.org/1fmh PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1fmh RCSB], [https://www.ebi.ac.uk/pdbsum/1fmh PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1fmh ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/GCN4_YEAST GCN4_YEAST] Is a transcription factor that is responsible for the activation of more than 30 genes required for amino acid or for purine biosynthesis in response to amino acid or purine starvation. Binds and recognize the DNA sequence: 5'-TGA[CG]TCA-3'.
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== Publication Abstract from PubMed ==
Residues of opposite charge often populate heptad positions g (heptad i on chain 1) and e' (heptad i + 1 on chain 2) in dimeric coiled coils and may stabilize the dimer by formation of interchain ion pairs. To investigate the contribution to stability of such electrostatic interactions we have designed a disulfide-linked heterodimeric zipper (AB zipper) consisting of the acidic chain Ac-E-VAQLEKE-VAQAEAE-NYQLEQE-VAQLEHE-CG-NH(2) and the basic chain Ac-E-VQALKKR-VQALKAR-NYAAKQK-VQALRHK-CG-NH(2) in which all e and g positions are occupied by either E or K/R to form a maximum of seven interhelical salt bridges. Temperature-induced denaturation experiments monitored by circular dichroism reveal a stable coiled coil conformation below 50 degrees C and in the pH range 1.2-8.0. Stability is highest at pH approximately 4.0 [DeltaG(U) (37 degrees C) = 5.18 +/- 0.51 kcal mol(-)(1)]. The solution structure of the AB zipper at pH 5.65 has been elucidated on the basis of homonuclear (1)H NMR data collected at 800 MHz [heavy atom rmsd's for the ensemble of 50 calculated structures are 0.47 +/- 0.13 A (backbone) and 0.95 +/- 0.16 A (all)]. Both chains of the AB zipper are almost entirely in alpha-helical conformation and form a superhelix with a left-handed twist. Overhauser connectivities reveal close contacts between g position residues (heptad i on chain 1) and residues d/f (heptad i on chain 1), residues a/d (heptad i + 1 on chain 1), and residue a' (heptad i + 1 on chain 2). Residues in position e (heptad i on chain 1) are in contact with residues a/b/d/f (heptad i on chain 1) and residue d' (heptad i on chain 2). These connectivities hint at a relatively defined alignment of the side chains across the helix interface. Partial H-bond formation between the functional groups of residues g and e'(+1) is observed in the calculated structures. NMR pH titration experiments disclose pK(a) values for Glu delta-carboxylate groups: 4.14 +/- 0.02 (E(1)), 4.82 +/- 0.07 (E(6)), 4.52 +/- 0.01 (E(8)), 4.37 +/- 0.03 (E(13)), 4.11 +/- 0.02 (E(15)), 4.41 +/- 0.07 (E(20)), 4.82 +/- 0.03 (E(22)), 4.65 +/- 0.04 (E(27)), 4.63 +/- 0.03 (E(29)), 4.22 +/- 0.02 (E(1)(')). By comparison with pK(a) of Glu in unfolded peptides ( approximately 4. 3 +/- 0.1), our pK(a) data suggest marginal or even unfavorable contribution of charged Glu to the stability of the AB zipper. The electrostatic energy gained from interhelical ion pairs is likely to be surpassed by hydrophobic energy terms upon protonation of Glu, due to increased hydrophobicity of uncharged Glu and, thus, better packing against apolar residues at the chain interface.

Interhelical ion pairing in coiled coils: solution structure of a heterodimeric leucine zipper and determination of pKa values of Glu side chains.,Marti DN, Jelesarov I, Bosshard HR Biochemistry. 2000 Oct 24;39(42):12804-18. PMID:11041845<ref>PMID:11041845</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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<div class="pdbe-citations 1fmh" style="background-color:#fffaf0;"></div>

==See Also==
*[[Gcn4 3D Structures|Gcn4 3D Structures]]
*[[Gnc4 3D Structures|Gnc4 3D Structures]]
== References ==
<references/>
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</StructureSection>
[[Category: Large Structures]]
[[Category: Saccharomyces cerevisiae S288C]]
[[Category: Bosshard HR]]
[[Category: Jelesarov I]]
[[Category: Marti DN]]