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Steric and hydrophobic determinants of the solubilities of recombinant sickle cell hemoglobins.
- Source :
-
Protein science : a publication of the Protein Society [Protein Sci] 1992 Jan; Vol. 1 (1), pp. 145-50. - Publication Year :
- 1992
-
Abstract
- Models for the structure of the fibers of deoxy sickle cell hemoglobin (Hb Hb S, beta 6 Glu-->Val) have been obtained from X-ray and electron microscopic studies. Recent molecular dynamics calculations of polymer formation give new insights on the various specific interactions between monomers. Site-directed mutagenesis with expression of the Hb S beta subunits in Escherichia coli provides the experimental tools to test these models. For Hb S, the beta 6 Val residue is intimately involved in a specific lateral contact, at the donor site, that interacts with the acceptor site of an adjacent molecule composed predominantly of the hydrophobic residues Phe 85 and Leu 88. Comparing natural and artificial mutants indicates that the solubility of deoxyHb decreases in relation to the surface hydrophobicity of the residue at the beta 6 position with Ile > Val > Ala. We also tested the role of the stereospecific adjustment between the donor and acceptor sites by substituting Trp for Glu at the beta 6 location. Among these hydrophobic substitutions and under our experimental conditions, only Val and Ile were observed to induce polymer formation. The interactions for the Ala mutant are too weak whereas a Trp residue inhibits aggregation through steric hindrance at the acceptor site of the lateral contact. Increasing the hydrophobicity at the axial contact between tetramers of the same strand also contributes to the stability of the double strand. This is demonstrated by associating the beta 23 Val-->Ile mutation at the axial contact with either the beta 6 Glu-->Val or beta 6 Glu-->Ile substitution in the same beta subunit.(ABSTRACT TRUNCATED AT 250 WORDS)
- Subjects :
- Alanine chemistry
Alanine genetics
Escherichia coli genetics
Glutamates chemistry
Glutamates genetics
Glutamic Acid
Humans
Isoleucine chemistry
Isoleucine genetics
Mutagenesis, Site-Directed
Oxygen metabolism
Protein Engineering
Recombinant Proteins chemistry
Solubility
Structure-Activity Relationship
Valine chemistry
Valine genetics
Hemoglobin, Sickle chemistry
Hemoglobin, Sickle genetics
Protein Conformation
Subjects
Details
- Language :
- English
- ISSN :
- 0961-8368
- Volume :
- 1
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- Protein science : a publication of the Protein Society
- Publication Type :
- Academic Journal
- Accession number :
- 1363932
- Full Text :
- https://doi.org/10.1002/pro.5560010114