1fmh

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(New page: 200px<br /><applet load="1fmh" size="450" color="white" frame="true" align="right" spinBox="true" caption="1fmh" /> '''NMR SOLUTION STRUCTURE OF A DESIGNED HETEROD...)
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'''NMR SOLUTION STRUCTURE OF A DESIGNED HETERODIMERIC LEUCINE ZIPPER'''<br />
'''NMR SOLUTION STRUCTURE OF A DESIGNED HETERODIMERIC LEUCINE ZIPPER'''<br />
==Overview==
==Overview==
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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.
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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.
==About this Structure==
==About this Structure==
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1FMH is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/ ] with ACE and NH2 as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1FMH OCA].
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1FMH is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/ ] with <scene name='pdbligand=ACE:'>ACE</scene> and <scene name='pdbligand=NH2:'>NH2</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1FMH OCA].
==Reference==
==Reference==
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:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=11041845 11041845]
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:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=11041845 11041845]
[[Category: Protein complex]]
[[Category: Protein complex]]
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[[Category: Bosshard, H.R.]]
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[[Category: Bosshard, H R.]]
[[Category: Jelesarov, I.]]
[[Category: Jelesarov, I.]]
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[[Category: Marti, D.N.]]
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[[Category: Marti, D N.]]
[[Category: ACE]]
[[Category: ACE]]
[[Category: NH2]]
[[Category: NH2]]
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[[Category: leucine zipper]]
[[Category: leucine zipper]]
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''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Sun Nov 25 00:02:45 2007''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:40:18 2008''

Revision as of 10:40, 21 February 2008

Image:1fmh.gif

1fmh

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NMR SOLUTION STRUCTURE OF A DESIGNED HETERODIMERIC LEUCINE ZIPPER

Overview

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.

About this Structure

1FMH is a Protein complex structure of sequences from [1] with and as ligands. Full crystallographic information is available from OCA.

Reference

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

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