1,721,108 research outputs found
Anion-linked polymerization of the tetrameric hemoglobin from Scapharca inaequivalvis. Characterization and functional relevance.
No full textRigidity of the heme pocket in the cooperative Scapharca hemoglobin homodimer and relation to the direct communication between hemes.
No full textThe distal heme pocket of Escherichia coli flavohemoglobin probed by infrared spectroscopy
No full textThe infrared absorption spectra of ferric cyanide and ferrous carbonmonoxy Escherichia coli flavohemoglobin have been measured in order to probe the fine structural properties of the distal. heme pocket, characterized by the presence of a tyrosine in position B10 and a glutamine in position E7. The stretching frequency of iron bound cyanide occurs at 2136 cm(-1), an unusually high value if compared to other heme proteins. The infrared spectrum of the CO bound derivative displays two peaks centered at 1960 cm(-1) and at 1909 cm(-1) respectively. (H2O)-H-2 effects have been studied in both the ferric cyanide and ferrous CO derivatives in order to establish the presence of a distal hydrogen bonding to the iron bound ligand. The observed isotope shifts indicate that in the ferric cyanide derivative a hydrogen bond is donated from a residue in the distal pocket to the biatomic ligand whereas in the ferrous carbon monoxy derivative only the 1909 cm(-1) component is most likely hydrogen bonded to the phenolic group of TyrB10
Flavohemoglobin: structure and reactivity.
No full textFlavohemoglobins (flavoHbs) are made of a globin domain fused with a ferredoxin reductaselike FAD- and NAD-binding modules. These proteins are widely represented among bacteria and yeasts and represent a most challenging research subject in view of their high reactivity both as reductases and as oxidases. The functional annotations of flavoHbs are still controversial, and different physiological roles that are linked to cell responses to oxidative and/or nitrosative stress have been proposed. The flavoHb from Escherichia coli (HMP) has been the object of a large number of investigations to unveil its physiological role in the framework of bacterial resistance to nitrosative stress. HMP expression has been demonstrated to respond to the presence of NO in the culture medium, and an explicit mechanism has been proposed that involves NO scavenging and its reduction to N2O under anaerobic conditions. In contrast to (or together with) the anaerobic NO-reductase activity, HMP has also been shown to be able to catalyze the oxidation of NO to NO3- (NO-dioxygenase activity) both in vivo and in vitro in the presence Of 02 and NADH. HMP has also been shown to be capable of catalyzing the reduction of several alkylhydroperoxide substrates into their corresponding alcohols using NADH as an electron donor. The alkylhydroperoxide reductase activity taken together with the unique lipid-binding properties of HMP suggests that this flavoHb may be involved in the repair of the lipid membrane oxidative damage generated during oxidative/ nitrosative stress
Cellular targeted label delivery system
No full textThe present invention relates to an isolated cellular targeted delivery system comprising a CD45+ leukocyte cell comprising within said cell a complex of one or more iron binding proteins and/or labels as well as methods for producing such isolated cellular targeted delivery system and uses of such system for therapy diagnosis and in particular for diagnosis of cancer, particularly metastatic cancer, in particular for therapy of cancer
The mutation K30D disrupts the only salt bridge at the subunit interface of the homodimeric hemoglobin from Scapharca inaequivalvis and changes the mechanism of cooperativity
No full textThe subunit interface of the homodimeric hemoglobin from Scapharca inaequivalvis, HbI, is stabilized by a network of interactions that involve several hydrogen-bonded structural water molecules, a hydrophobic patch, and a single, symmetrical salt bridge between residues Lys-30 and Asp-89. Upon mutation of Lys-30 to Asp, the interface is destabilized markedly. Sedimentation equilibrium and velocity experiments allowed the estimate of the dimerization constants for the unliganded (K-1,K-2 D = 8 x 10(4) M-1) and for the CO-bound (K-1,K-2 L = 1 x 10(3) M-1) and oxygenated (K-1,K-2 L = 70 M-1) derivatives. For the oxygenated derivative, the destabilization of the subunit interface with respect to native HbI corresponds to about 8 kcal/mol, an unexpectedly high figure. In the K30D mutant, at variance with the native protein, oxygen affinity and cooperativity are strongly dependent on protein concentration. At low protein concentrations (e.g. 1.2 x 10(-5) M heme), at which the monomeric species becomes significant also in the unliganded derivative, oxygen affinity increases and cooperativity decreases. At protein concentrations where both derivatives are dimeric (e.g. 3.3 x 10(-3) M heme), both cooperativity and oxygen affinity decrease. Taken together, the experimental data indicate that in the K30D mutant, the mechanism of cooperativity is drastically altered and is driven by a ligand-linked monomer-dimer equilibrium rather than being based on a direct heme-heme communication as in native HbI
PROXIMAL AND DISTAL EFFECTS ON THE COORDINATION CHEMISTRY OF FERRIC SCAPHARCA HOMODIMERIC HEMOGLOBIN AS REVEALED BY HEME POCKET MUTANTS
No full textMetastable CO binding sites in the photoproduct of a novel cooperative dimeric hemoglobin.
No full textThe infrared absorption spectrum of the CO-photoproduct from Scapharca inaequivalvis hemoglobin (Hbl) at 10 K yields only a single line in the "B" state region at 2132 cm-1. This is the same frequency as the B1 line observed in photodissociated vertebrate HbCO and MbCO. No evidence was found for the B2 line detected in vertebrate hemoglobins and myoglobin in the 21182120 cm-1 region. These data demonstrate that the protein does not have the same conformationally accessible ligand-binding sites as do vertebrate hemoglobins and myoglobins. The absence of the B2 line indicates that only a single weak site is accessible to the photolyzed CO molecule. These results are in accord with geminate rebinding experiments and ligand escape pathway calculations which have shown that the distal properties of Hbl are distinct from those of tetrameric hemoglobins and vertebrate myoglobins
- …
