Structures of deoxy and oxy hemerythrin at 2.0 Å resolution

Holmes, Michael; Trong, I. Le; Turley, S.; Sieker, L.C.; Stenkamp, Ronald E.

doi:10.1016/0022-2836(91)90703-9

Cited by 212 publications

(187 citation statements)

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“…hemerythrin and myohemerythrin [18]. The mutational evidence on AlkB presented in this study is consistent with the hypothesis that these residues are involved in coordination of the diiron center, because substitution of any of the eight conserved histidines resulted in complete loss of measurable activity, while substitution of three adjacent non-conserved histidine residues resulted in modest reductions of activity compared to those of wild type.…”

Section: Discussionsupporting

confidence: 76%

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Evidence linking the Pseudomonas oleovorans alkane ω‐hydroxylase, an integral membrane diiron enzyme, and the fatty acid desaturase family

Shanklin

Whittle

2003

FEBS Letters

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Pseudomonas oleovorans alkane g g-hydroxylase (AlkB) is an integral membrane diiron enzyme that shares a requirement for iron and oxygen for activity in a manner similar to that of the non-heme integral membrane desaturases, epoxidases, acetylenases, conjugases, ketolases, decarbonylase and methyl oxidases. No overall sequence similarity is detected between AlkB and these desaturase-like enzymes by computer algorithms; however, they do contain a series of histidine residues in a similar relative positioning with respect to hydrophobic regions thought to be transmembrane domains. To test whether these conserved histidine residues are functionally equivalent to those of the desaturase-like enzymes we used scanning alanine mutagenesis to test if they are essential for activity of AlkB. These experiments show that alanine substitution of any of the eight conserved histidines results in complete inactivation, whereas replacement of three non-conserved histidines in close proximity to the conserved residues, results in only partial inactivation. These data provide the ¢rst experimental support for the hypotheses: (i) that the histidine motif in AlkB is equivalent to that in the desaturase-like enzymes and (ii) that the conserved histidine residues play a vital role such as coordinating the Fe ions comprising the diiron active site.

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Section: Discussionsupporting

confidence: 76%

“…Class I contains the soluble O 2 -carrying proteins hemerythrin and myohemerythrin, coordinated primarily via nitrogen ligands [18]. Class II includes the soluble methane monooxygenase, ribonucleotide reductase and soluble plant v 9 -desaturases in which the diiron center is primarily coordinated via oxygen ligands [11,19^21].…”

Section: Introductionmentioning

confidence: 99%

Evidence linking the Pseudomonas oleovorans alkane ω‐hydroxylase, an integral membrane diiron enzyme, and the fatty acid desaturase family

Shanklin

Whittle

2003

FEBS Letters

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“…3) for the M2myoHrs indicate a considerable degree of unfolding cooperativity, in contrast to the behavior of apomyoHr. The lack of appreciable unfolding cooperativity in apomyoHr can be attributed to fewer interhelical interactions than are known to occur in the native proteins (9,31). The reduced number of interhelical interactions would be required to accommodate solvation of the seven iron ligand residues, which are all quite polar (see Scheme I).…”

Section: Discussionmentioning

confidence: 99%

“…Hr and myoHr are structurally well-characterized and their biological activity-i.e., 02 binding-can be readily observed and quantitated. The secondary, tertiary, and diiron site structures of the subunits in Hr and myoHr (shown schematically in Scheme I) are quite similar to each other (7)(8)(9). Though myoHr is monomeric, Hr is usually octameric; thus, comparisons of the refolding of Hr vs. myoHr would allow assessments of the effects of intersubunit interactions on refolding of two nearly identical protein structures.…”

Section: Scheme Imentioning

confidence: 99%

Metal substitutions at the diiron sites of hemerythrin and myohemerythrin: contributions of divalent metals to stability of a four-helix bundle protein.

Zhang

Kurtz

1992

Proc. Natl. Acad. Sci. U.S.A.

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A general method is described for substitution of Mn(II) and Co(ll) into the diiron sites of hemerythrin and myohemerythrin. Characterizations of these metalsubstituted proteins show that their stAcures closely resemble those ofthe native proteins. In particular, the four-helix bundle strcture appears to be maintained. The apomyohemerythrin retains most of the native helix content but is considerably less stable to denaturation than are the metal-containing proteins.The relative afnities of M(l) for apohemery thrn-nmely, Co > Fe > Mn-parallel the stabilities of the M2myoheme-rythrlns to denaturation by gdinium chloride. These results indicate that for myohemerythrin (i) the majority of the helical s re found in the native protein does not require incorporation of M(II) and (ii) stabilization of the native structure relative to the fully unfolded structure appears to be due predominantly to M(H)- Although the pathways by which proteins fold into their native structures in vivo are difficult to examine directly, the large number of in vitro refolding studies provides a useful framework for understanding in vivo folding (1-5). Prosthetic groups in general are known to stabilize the native folded structure, but only a few examinations of the role of metal ions in nonheme protein folding have been undertaken (e.g., see ref.3), despite the large and rapidly growing number of nonheme metalloproteins that can be reconstituted by addition of metal ions (6). Scheme IFor several reasons, the nonheme iron 02-carrying proteins hemerythrin (Hr) and myohemerythrin (myoHr) are excellent candidates for examining the process of nonheme metal ion insertion and its connection to protein folding and stability. Hr and myoHr are structurally well-characterized and their biological activity-i.e., 02 binding-can be readily observed and quantitated. The secondary, tertiary, and diiron site structures of the subunits in Hr and myoHr (shown schematically in Scheme I) are quite similar to each other (7-9). Though myoHr is monomeric, Hr is usually octameric; thus, comparisons of the refolding of Hr vs. myoHr would allow assessments of the effects of intersubunit interactions on refolding of two nearly identical protein structures. The subunit in Hr and myoHr has a "four-helix bundle" structure with ==70%o a-helix and contains a diiron active site that binds one molecule of 02 at Fe2. The four-helix bundle is a structural motif found in several proteins (ref. 10 and references therein), but only in the case of cytochrome b562 has an investigation of the role of the prosthetic group in protein folding and stability recently been initiated (11). The two iron atoms comprising the active site in Hr and myoHr are ligated by a total of seven amino acid side chains with either one or two ligand residues from each of the four helical regions. In effect the diiron site cross-links the four helices (see Scheme I). For this reason and because of the relatively small sizes of Hr and myoHr (Mr "13,500 and ='13,900, respectively, per diiron site), ...

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“…In biological systems, a µ-hydroxo-bis(µ-carboxylato) diiron(II) structure was found in the active site of hemerythrin [1]. Previously, [2].…”

Section: Bis(µ-carboxylato) Bridge a µ-Phenoxo-bis(µ-carboxylato)mentioning

confidence: 99%

Conformational Analysis and Computational Modeling of a µ-Phenoxo-bis(µ-carboxylato)dizinc(II) Complex

Sakiyama

Suzuki

Yamaguchi

2011

J. Comput. Chem. Jpn.

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Structures of deoxy and oxy hemerythrin at 2.0 Å resolution

Cited by 212 publications

References 13 publications

Evidence linking the Pseudomonas oleovorans alkane ω‐hydroxylase, an integral membrane diiron enzyme, and the fatty acid desaturase family

Evidence linking the Pseudomonas oleovorans alkane ω‐hydroxylase, an integral membrane diiron enzyme, and the fatty acid desaturase family

Metal substitutions at the diiron sites of hemerythrin and myohemerythrin: contributions of divalent metals to stability of a four-helix bundle protein.

Conformational Analysis and Computational Modeling of a µ-Phenoxo-bis(µ-carboxylato)dizinc(II) Complex

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