1v07: Difference between revisions
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[[Category: oxygen affinity of c.lacteus mini-hemoglobin]] | [[Category: oxygen affinity of c.lacteus mini-hemoglobin]] | ||
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Revision as of 18:12, 5 November 2007
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CRYSTAL STRUCTURE OF THRE11VAL MUTANT OF THE NERVE TISSUE MINI-HEMOGLOBIN FROM THE NEMERTEAN WORM CEREBRATULUS LACTEUS
OverviewOverview
The mini-hemoglobin from Cerebratulus lacteus (CerHb) belongs to a class, of globins containing the polar Tyr-B10/Gln-E7 amino acid pair that, normally causes low rates of O2 dissociation and ultra-high O2 affinity, which suggest O2 sensing or NO scavenging functions. CerHb, however, has, high rates of O2 dissociation (kO2 = 200-600 s(-1)) and moderate O2, affinity (KO2) approximately 1 microm(-1)) as a result of a third polar, amino acid in its active site, Thr-E11. When Thr-E11 is replaced by Val, kO2 decreases 1000-fold and KO2 increases 130-fold at pH 7.0, 20 degrees, C. The mutation also shifts the stretching frequencies of both heme-bound, and photodissociated CO, indicating marked changes of the electrostatic, field at the active site. The crystal structure of Thr-E11 --> Val CerHbO2, at 1.70 A resolution is almost identical to that of the wild-type protein, (root mean square deviation of 0.12 A). The dramatic functional and, spectral effects of the Thr-E11 --> Val mutation are due exclusively to, changes in the hydrogen bonding network in the active site. Replacing, Thr-E11 with Val "frees" the Tyr-B10 hydroxyl group to rotate toward and, donate a strong hydrogen bond to the heme-bound ligand, causing a, selective increase in O2 affinity, a decrease of the rate coefficient for, O2 dissociation, a 40 cm(-1) decrease in nuCO of heme-bound CO, and an, increase in ligand migration toward more remote intermediate sites.
About this StructureAbout this Structure
1V07 is a Single protein structure of sequence from Cerebratulus lacteus with SO4, HEM and OXY as ligands. Structure known Active Site: AC1. Full crystallographic information is available from OCA.
ReferenceReference
Thr-E11 regulates O2 affinity in Cerebratulus lacteus mini-hemoglobin., Pesce A, Nardini M, Ascenzi P, Geuens E, Dewilde S, Moens L, Bolognesi M, Riggs AF, Hale A, Deng P, Nienhaus GU, Olson JS, Nienhaus K, J Biol Chem. 2004 Aug 6;279(32):33662-72. Epub 2004 May 25. PMID:15161908
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