The Solution Structure of the Recombinant Hemoglobin from the Cyanobacterium Synechocystis sp. PCC 6803 in its Hemichrome State

Falzone, Christopher J.; Vu, B. Christie; Scott, Nancy L.; Lecomte, Juliette T. J.

doi:10.1016/s0022-2836(02)01093-8

Cited by 62 publications

(76 citation statements)

References 65 publications

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“…Alternatively, the multiple hexacoordinated states may account for multiple functions in the same molecule. Hexacoordinated Hbs are observed in unicellular eukaryotes [17], plants [49], invertebrates [50], and in some tissues of higher vertebrates [48,51], but only a few cases have been examined and reported in the literature for bacterial 2/2 Hbs [52][53][54][55]. The physiological role of these hexacoordinated Hbs is not well understood.…”

Section: Discussionmentioning

confidence: 99%

The peculiar heme pocket of the 2/2 hemoglobin of cold-adapted Pseudoalteromonas haloplanktis TAC125

et al. 2010

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The genome of the cold-adapted bacterium Pseudoalteromonas haloplanktis TAC125 contains multiple genes encoding three distinct monomeric hemoglobins exhibiting a 2/2 a-helical fold. In the present work, one of these hemoglobins is studied by resonance Raman, electronic absorption and electronic paramagnetic resonance spectroscopies, kinetic measurements, and different bioinformatic approaches. It is the first cold-adapted bacterial hemoglobin to be characterized. The results indicate that this protein belongs to the 2/2 hemoglobin family, Group II, characterized by the presence of a tryptophanyl residue on the bottom of the heme distal pocket in position G8 and two tyrosyl residues (TyrCD1 and TyrB10). However, unlike other bacterial hemoglobins, the ferric state, in addition to the aquo hexacoordinated high-spin form, shows multiple hexacoordinated low-spin forms, where either TyrCD1 or TyrB10 can likely coordinate the iron. This is the first example in which both TyrCD1 and TyrB10 are proposed to be the residues that are alternatively involved in heme hexacoordination by endogenous ligands.

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Section: Discussionmentioning

confidence: 99%

The peculiar heme pocket of the 2/2 hemoglobin of cold-adapted Pseudoalteromonas haloplanktis TAC125

et al. 2010

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“…However, a 3-7 amino acid insertion located between the C-and E-helices, is invariantly found in group III 2/2HbPs (2,17). Such elongation of the CD region has implications on the span of the C-and E-helices and on the 3 10 helical character of helix C. Notably, after extensive three-dimensional structure comparisons, the overall fold of group III 2/2HbP appears equally different in its C a trace from group I and group II (Fig. 2B).…”

Section: The Truncated Hb 2/2 Globin Foldmentioning

confidence: 99%

Protein structure in the truncated (2/2) hemoglobin family

Pesce¹,

Nardini

Milani

et al. 2007

IUBMB Life

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The discovery of protein sequences belonging to the widespread 'truncated hemoglobin' family has been followed in the last few years by extensive analyses of their three‐dimensional structures. Truncated hemoglobins can be classified in three main groups, in light of their overall structural properties. The three groups adopt a 2‐on‐2 α‐helical sandwich fold, based on four main α‐helices of the classical 3‐on‐3 α‐helical sandwich found in vertebrate and invertebrate globins. Each of the three groups displays sequence and structure specific features. Among these, a protein matrix tunnel system is typical of group I, a Trp residue at the G8 topological site is conserved in groups II and III, and residue TyrB10 is almost invariant in the three groups. Despite sequence variability in the heme distal site region, a strongly intertwined, but varied, network of hydrogen bonds stabilizes the heme ligand in the three protein groups. Fine mechanisms of ligand recognition and stabilization may vary based on group‐specific distal site residues and on differing ligand diffusion pathways to the heme. Taken together, the structural considerations here presented underline that 'truncated hemoglobins' result from careful editing of the 3‐on‐3 α‐helical globin sandwich fold, rather than from simple 'truncation' events. Thus, '2/2Hb' appears the most proper term to concisely address this protein family.

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“…The higher pK a of the main transition obscured the second transition. In both proteins, the Hill coefficient suggested that release was coupled to at least three protonation events, which would arise from His46, His70, and a third group, possibly the heme 7-propionate as a hydrogen bond was noted to Lys42 (34).…”

Section: Heme Release From A69s S6803 Rhb-r Upon Solution Acidificationmentioning

confidence: 99%

“…Minor deviations were also observed for the heme group. Peripheral substituents (protons in α to PPIX ring) experienced an upfield shift on pyrrole A and C and a downfield shift on pyrrole B and D. In previous work, the paramagnetic shift of the methyl groups was used to assess the orientation of the axial histidines in the wild-type protein (34). The same heuristic approach (57) applied to the A69S variant showed that the shifts were consistent with a rotation of a few degrees of the bisector of the two histidine planes and a slight decrease in the angle between the two imidazole planes.…”

Section: Structurementioning

confidence: 99%

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Proximal Influences in Two-on-Two Globins: Effect of the Ala69Ser Replacement on Synechocystis sp. PCC 6803 Hemoglobin

Knappenberger

Kuriakose

et al. 2006

Biochemistry

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The cyanobacterium Synechocystis sp. PCC 6803 (S6803) expresses a two-on-two globin in which His46 (distal side) and His70 (proximal) function as heme iron axial ligands. His46 can be displaced by O 2 , CO, and CN − , among others, whereas His70 is not labile under native conditions. The residue preceding the proximal histidine has been implicated in controlling globin axial ligand reactivity; the details of the mechanism, however, are not well understood, and little information exists for bis-histidyl hexacoordinate proteins. In many vertebrate hemoglobins and in the Synechocystis protein, the position is occupied by an alanine whereas, in myoglobins, it is a serine involved in an intricate hydrogen bond network. We examined the role of Ala69 in S6803 hemoglobin through the effects of an Ala → Ser replacement. The substitution resulted in minor structural perturbations, but the holoprotein's response to temperature-, urea-, and acid-induced denaturation was measurably affected. Enhanced three-state behavior was manifested in the decoupling of heme binding and secondary structure formation. Urea-gradient gel experiments revealed that the stability of the apoprotein was unchanged by the replacement and that a slight alteration of the folding kinetics occurred in the holoproteins. Cyanide-binding experiments were performed to assess trans effects. The apparent rate constant for association decreased two-fold upon Ala69Ser replacement. This deceleration was attributed to a change in the lifetime of a state containing a decoordinated His46. The results demonstrated that, as in vertebrate globins and leghemoglobin, proximal influences operate to determine fundamental dynamic and thermodynamic properties of the protein.Keywords truncated hemoglobin; 2-on-2 globin; hexacoordinate hemoglobin; urea-gradient gel; heme binding; thermodynamic stabilityIron protoporphyrin IX (Fe-PPIX) 1 serves as a cofactor in a large number of essential proteins. In the absence of covalent attachment to the protein matrix via protoporphyrin substituents, the contact between Fe(II)-PPIX (or b heme) and the protein is limited to ligation bond(s) to the iron, hydrogen bonding, van der Waals and electrostatic interactions, and hydrophobic † This study was supported by National Science Foundation grants MCB-091182 and MCB-0349409, National Institutes of Health grant GM-054217, and NASA grant NNG04GN33H (DAV).* To whom correspondence should be addressed. Tel: (814) NIH Public Access Author ManuscriptBiochemistry. Author manuscript; available in PMC 2008 September 11. forces. The affinity for the heme group and its chemical properties, such as redox potential, ability to bind various ligands, and propensity for generating reactive oxygen species, are strictly controlled by the protein environment.In many b hemoproteins the iron is endogenously hexacoordinated, with the axial positions of its octahedral geometry filled by two histidine side chains (1). A well-known example is cytochrome b 5 , an electron-transfer protein that does not bind...

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The Solution Structure of the Recombinant Hemoglobin from the Cyanobacterium Synechocystis sp. PCC 6803 in its Hemichrome State

Cited by 62 publications

References 65 publications

The peculiar heme pocket of the 2/2 hemoglobin of cold-adapted Pseudoalteromonas haloplanktis TAC125

The peculiar heme pocket of the 2/2 hemoglobin of cold-adapted Pseudoalteromonas haloplanktis TAC125

Protein structure in the truncated (2/2) hemoglobin family

Proximal Influences in Two-on-Two Globins: Effect of the Ala69Ser Replacement on Synechocystis sp. PCC 6803 Hemoglobin

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