1fmh
From Proteopedia
| Line 1: | Line 1: | ||
[[Image:1fmh.gif|left|200px]] | [[Image:1fmh.gif|left|200px]] | ||
| - | + | <!-- | |
| - | + | The line below this paragraph, containing "STRUCTURE_1fmh", creates the "Structure Box" on the page. | |
| - | + | You may change the PDB parameter (which sets the PDB file loaded into the applet) | |
| - | + | or the SCENE parameter (which sets the initial scene displayed when the page is loaded), | |
| - | + | or leave the SCENE parameter empty for the default display. | |
| - | + | --> | |
| - | | | + | {{STRUCTURE_1fmh| PDB=1fmh | SCENE= }} |
| - | | | + | |
| - | + | ||
| - | }} | + | |
'''NMR SOLUTION STRUCTURE OF A DESIGNED HETERODIMERIC LEUCINE ZIPPER''' | '''NMR SOLUTION STRUCTURE OF A DESIGNED HETERODIMERIC LEUCINE ZIPPER''' | ||
| Line 19: | Line 16: | ||
==About this Structure== | ==About this Structure== | ||
| - | 1FMH is a [[Protein complex]] structure | + | 1FMH is a [[Protein complex]] structure. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1FMH OCA]. |
==Reference== | ==Reference== | ||
| Line 27: | Line 24: | ||
[[Category: Jelesarov, I.]] | [[Category: Jelesarov, I.]] | ||
[[Category: Marti, D N.]] | [[Category: Marti, D N.]] | ||
| - | [[Category: | + | [[Category: Coiled coil]] |
| - | [[Category: | + | [[Category: Inter-helical ion pairing]] |
| - | [[Category: | + | [[Category: Leucine zipper]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 16:30:15 2008'' | |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 13:30, 2 May 2008
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. 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 Page seeded by OCA on Fri May 2 16:30:15 2008
