Mutagenesis of histidine 26 demonstrates the importance of loop‐loop and loop‐protein interactions for the function of iso‐1‐cytochrome c

Fetrow, Jacquelyn S.; Dreher, Ulrike; Wiland, Debra J.; Boose, Terry L.

doi:10.1002/pro.5560070417

Cited by 15 publications

(18 citation statements)

References 69 publications

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“…The H33N and H39Q mutations do not affect the stability of iso‐1‐cyt c 15, 28. Mutation of His 26 is known to destabilize various cytochromes c 15, 28–30. Thus, the H26N mutation is expected to dominate changes in the stability of the TM variant.…”

Section: Resultsmentioning

confidence: 97%

Compressing the free energy range of substructure stabilities in iso‐1‐cytochrome c

Duncan¹,

Williams²,

Bowler³

2009

Protein Science

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Evolutionary conservation of substructure architecture between yeast iso-1-cytochrome c and the well-characterized horse cytochrome c is studied with limited proteolysis, the alkaline conformational transition and global unfolding with guanidine-HCl. Mass spectral analysis of limited proteolysis cleavage products for iso-1-cytochrome c show that its least stable substructure is the same as horse cytochrome c. The limited proteolysis data yield a free energy of 3.8 6 0.4 kcal mol 21 to unfold the least stable substructure compared with 5.05 6 0.30 kcal mol The tight free energy spacing of the yeast cytochrome c substructures suggests that its folding has more branch points than for horse cytochrome c. Studies on a variant of iso-1-cytochrome c with an H26N mutation indicate that the least and most stable substructures unfold sequentially and the two least stable substructures unfold independently as for horse cytochrome c. Thus, important aspects of the substructure architecture of horse cytochrome c, albeit compressed energetically, are preserved evolutionally in yeast iso-1-cytochrome c.

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Section: Resultsmentioning

confidence: 97%

Compressing the free energy range of substructure stabilities in iso‐1‐cytochrome c

Duncan¹,

Williams²,

Bowler³

2009

Protein Science

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“…As noted previously, His 26 is a highly conserved residue in cytochrome c. The residue is a part of a hydrogen bond network involving Asn 31 and Glu 44 and is a stabilizing factor in the protein (29). His 26 and Tyr 67 interact anticooperatively, producing a negative ∆ 2 G int in both the Asn 52 and the Ile 52 contexts.…”

Section: Possible Effects Of Mutations In the Actm Variant Relative Tmentioning

confidence: 90%

Role of Hydrogen Bond Networks and Dynamics in Positive and Negative Cooperative Stabilization of a Protein

Redzic

Bowler

2005

Biochemistry

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Cooperativity mediated through hydrogen bond networks in yeast iso-1-cytochrome c was studied using a thermodynamic triple mutant cycle. Three known stabilizing mutations, Asn 26 to His, Asn 52 to Ile, and Tyr 67 to Phe, were used to construct the triple mutant cycle. The side chain of His 26, a wild-type residue, forms two hydrogen bonds that bridge two substructures of the wild-type protein, and Tyr 67 and Asn 52 are part of an extensive buried hydrogen bond network. The stabilities of all variants in the triple mutant cycle were determined by guanidine hydrochloride denaturation methods and used to determine the pairwise, Delta(2)G(int), and triple interaction energies. His 26 and Ile 52 interact cooperatively (Delta(2)G(int) is 1-2 kcal/mol), whereas the two other pairs of mutations interact anticooperatively (Delta(2)G(int) is -0.5 to -1.5 kcal/mol). Previously reported structural data for iso-1-cytochrome c variants containing these mutations show that changes in the strength of the His 26 to Glu 44 hydrogen bond, apparently caused by changes in main chain dynamics, provide a mechanism for the long distance (His 26 to Phe 67 and His 26 to Ile 52) propagation of pairwise interaction energies. Opposing changes in the strength of the His 26 to Glu 44 hydrogen bond caused by the N52I and Y67F mutations generate a negative triple interaction energy (-0.9 +/-0.7 kcal/mol) that combined with cancellation of cooperative and anticooperative pairwise interactions produce apparent additivity for the stabilizing effects of the single mutations in the triple mutant variant.

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“…16 This conformation change was proposed to be initiated by protonation of His26, 17,18 which H-bonds to Pro44, a residue at the tip of a long omega loop (40’s Ω loop) (Figure 1). This loop was characterized by Englander and coworkers 19,20 as the least stable cooperative unfolding unit (‘foldon’) in cyt c. It is anchored at its other end by a short β-sheet ‘neck’, which we suggested could extend into the loop itself, when the His26-Pro44 H-bond is broken.…”

Section: Introductionmentioning

confidence: 99%

His26 Protonation in Cytochrome c Triggers Microsecond β-Sheet Formation and Heme Exposure: Implications for Apoptosis

Balakrishnan

Spiro

2012

J. Am. Chem. Soc.

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Cytochrome c unfolds locally and reversibly upon heating at pH 3. UV resonance Raman (UVRR) spectra reveal that instead of producing unordered structure, unfolding converts turns and some helical elements to β-sheet. It also disrupts the Met80-heme bond, and was earlier shown to induce peroxidase activity. Aromatic residues that are H-bonded to a heme propionate (Trp59 and Tyr48) alter their orientation, indicating heme displacement. T-jump/UVRR measurements give time constants of 0.2, 3.9 and 67 µs for successive phases of β-sheet formation and concomitant reorientation of Trp59. UVRR spectra reveal protonation of histidines, and specifically of His26, whose H-bond to Pro44 anchors the 40s Ω loop; this loop is known to be the least stable ‘foldon’ in the protein. His26 protonation is proposed to disrupt its H-bond with Pro44, triggering the extension of a short β-sheet segment at the ‘neck’ of the 40s Ω loop into the loop itself and back into the 60’s and 70’s helices. The secondary structure change displaces the heme via H-bonds from residues in the growing β-sheet, thereby exposing it to exogenous ligands, and inducing peroxidase activity. This unfolding mechanism may play a role in cardiolipin peroxidation by cyt c during apoptosis.

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Mutagenesis of histidine 26 demonstrates the importance of loop‐loop and loop‐protein interactions for the function of iso‐1‐cytochrome c

Cited by 15 publications

References 69 publications

Compressing the free energy range of substructure stabilities in iso‐1‐cytochrome c

Compressing the free energy range of substructure stabilities in iso‐1‐cytochrome c

Role of Hydrogen Bond Networks and Dynamics in Positive and Negative Cooperative Stabilization of a Protein

His26 Protonation in Cytochrome c Triggers Microsecond β-Sheet Formation and Heme Exposure: Implications for Apoptosis

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