Flexibility and nucleation in sickle hemoglobin.

Val mutation of sickle hemoglobin (HbS) plus beta73 Asp-->Asn. By electron microscopy we find it forms crystals, rather than the wrapped multistranded fibers seen in HbS. Fourier transforms of the crystals yield unit cell parameters indistinguishable from crystals of HbS. Differential interference contrast (DIC) microscopy and birefringence also show crystal formation rather than the polymers or domains seen for HbS, while the growth patterns showed radiating crystal structures rather than simple linear crystalline forms. The solubility of the assembly was measured using a photolytic micromethod over a temperature range of 17-31 degrees C in 0.15 M phosphate buffer and found to be essentially the same as that of fibers of HbS. The assembly kinetics were observed by photolysis of the carbon monoxide derivative, and the mass of assembled hemoglobin was found to grow exponentially, with onset times that were stochastically distributed for small volumes. The stochastic onset of assembly showed strong concentration dependence, similar to but slightly greater than that seen in sickle hemoglobin nucleation. These observations suggest that like HbS, HbC-Harlem assembly proceeds by a homogeneous nucleation process, followed by heterogeneous nucleation. However, relative to HbS, both homogeneous and heterogeneous nucleation are suppressed by almost 11 orders of magnitude. The slowness of nucleation can be reconciled with the similarity of the solubility to HbS by an increase in contact energy coupled with a decrease in vibrational entropy recovered on assembly. This also explains the linearity of the double-strands, and agrees with the chemical nature of the structural replacement.
(Copyright 2001 Academic Press.) -->
Grant Information: HL 38632 United States HL NHLBI NIH HHS; HL 57549 United States HL NHLBI NIH HHS; HL 58512 United States HL NHLBI NIH HHS; HL 58879 United States HL NHLBI NIH HHS; HL22654 United States HL NHLBI NIH HHS
Substance Nomenclature: 0 (Biopolymers)
9008-00-8 (Hemoglobin C)
9034-57-5 (hemoglobin C-Harlem)
Entry Date(s): Date Created: 20011206 Date Completed: 20020214 Latest Revision: 20071114
Update Code: 20240829
DOI: 10.1006/jmbi.2001.5163
PMID: 11734002
Autor: Ivanova M; Department of Physics, Drexel University, Philadelphia, PA 19104, USA., Jasuja R, Krasnosselskaia L, Josephs R, Wang Z, Ding M, Horiuchi K, Adachi K, Ferrone FA
Jazyk: angličtina
Zdroj: Journal of molecular biology [J Mol Biol] 2001 Dec 07; Vol. 314 (4), pp. 851-61.
DOI: 10.1006/jmbi.2001.5163
Abstrakt: We have studied the self-assembly of Hemoglobin C-Harlem (HbC-Harlem), a double mutant of hemoglobin that possesses the beta6 Glu-->Val mutation of sickle hemoglobin (HbS) plus beta73 Asp-->Asn. By electron microscopy we find it forms crystals, rather than the wrapped multistranded fibers seen in HbS. Fourier transforms of the crystals yield unit cell parameters indistinguishable from crystals of HbS. Differential interference contrast (DIC) microscopy and birefringence also show crystal formation rather than the polymers or domains seen for HbS, while the growth patterns showed radiating crystal structures rather than simple linear crystalline forms. The solubility of the assembly was measured using a photolytic micromethod over a temperature range of 17-31 degrees C in 0.15 M phosphate buffer and found to be essentially the same as that of fibers of HbS. The assembly kinetics were observed by photolysis of the carbon monoxide derivative, and the mass of assembled hemoglobin was found to grow exponentially, with onset times that were stochastically distributed for small volumes. The stochastic onset of assembly showed strong concentration dependence, similar to but slightly greater than that seen in sickle hemoglobin nucleation. These observations suggest that like HbS, HbC-Harlem assembly proceeds by a homogeneous nucleation process, followed by heterogeneous nucleation. However, relative to HbS, both homogeneous and heterogeneous nucleation are suppressed by almost 11 orders of magnitude. The slowness of nucleation can be reconciled with the similarity of the solubility to HbS by an increase in contact energy coupled with a decrease in vibrational entropy recovered on assembly. This also explains the linearity of the double-strands, and agrees with the chemical nature of the structural replacement.
(Copyright 2001 Academic Press.)
Databáze: MEDLINE
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