Myoglobin hydrophobic interactions

Imately 65 X 55 X 50 It Is composed of four polypeptide chains each resembling quite closely the myoglobin chain The three dimensional structure of the subunits Is held together by weak noncovalent bonds The polar amino acid side chains are In contact with the solvent, and the nonpolar residues are located In the Interior of the molecule or In regions which form the contacts between chains The heme group Is located In a pocket In each chain residues In contact with heme are Invariable ( e are the same In different mammalian hemoglobins) and the bonds between heme and chain are hydrophobic Interactions Contacts between like chains (a-a are... 

Mixture of proteins (Myoglobin, Ovalbumin, Lysozyme and Chymotrypsinogen) Purification Hydrophobic Interaction [52]... 

Location of polar and nonpolar amino acid residues The interior of the myoglobin molecule is composed almost entirely of nonpolar amino acids. They are packed closely together, forming a structure stabilized by hydrophobic interactions between these clustered residues (see p. 19). In contrast, charged amino acids are located almost exclusively on the surface of the molecule, where they can form hydrogen bonds, with each other and with water. 

Following the original work by Kauzmann on hydrophobic interactions and the determinations of the structures of myoglobin and hemoglobin, it was stated, and is still stated frequently (despite evidence to the contrary), that hydrophobic residues are buried in the interior of proteins and hydrophilic residues are exposed to solvent water. It was first shown by Klotz (1970 see also Lee and Richards, 1971) that a substantial proportion of the exposed solvent-accessible surface area of proteins is composed of nonpolar groups. This matter has been stressed in lectures for many years by one of the authors (H. McK.) (for a discussion of various approaches to this problem, see Edsall and McKenzie, 1983). In the case of lysozyme, a substantial proportion of the hydrophobic residues Leu, Val, He, Ala, Gly, Phe, Tyr, Trp, Met, and Pro are either fully exposed to solvent or at least have some atoms that are solvent accessible. Examples of hydrophobic residues that are surface exposed are Val-2, Phe-3, Leu-17, Phe-34, Leu-75, Trp-123, Pro-70, and Pro-79, with Trp-62, Trp-63, Ile-98, Trp-108, and Val-109 being on the surface of the cleft. Examples of the least-exposed ionizable side chains are Asp-66, Asp-52, Tyr-53, His-15, and Glu-35. 

Figure 7 Correlation of plateau values with protein surface hydrophobicity (from hydrophobic interaction chromatography data) for the adsorption of egg-white lysozyme ( ), bovine pancrease ribonuclease (A), a-lact-albumin (x), sperm whale myoglobin ( ), and superoxide dismutase ( ) on negatively charged polystyrene in 50 mM KCI at 25°C and pH equal to pi of each protein. (From Ref. 17. Reprinted with permission.)...

The active site in myoglobin is a heme tightly bound to the proteins through about 80 hydrophobic interactions as well as by one close histidine and one more remote histidine interaction with the central iron ion. The unsymmetrical substitution with two imidazole ligands produces a high-spin Fe(II) ion with relatively high... 

Hydrophobic side chains of phenylalanine, alanine, valine, leucine, isoleucine, and methionine are clustered in the interior of the molecule, where they are shielded from contact with water. Hydrophobic interactions are a major factor in directing the folding of the polypeptide chain of myoglobin into this compact, three-dimensional shape. 

Figure 11. Separation of a protein mixture by hydrophobic interaction chromatography using a TSKgel Phenyl-5PW column. Column, 7.5 cm x 7.5 mm eluant A, 0.1 M phosphate buffer, pH 7.0 + 1.7 M (NH4)2S04i eluant B. 0.1 M phosphate buffer, pH 7.0 A — B 60 min linear gradient flow-rate, 1 ml/min detector, UV at 280 nm. Peaks (1) cytochrome c (2) myoglobin (3) ribonuclease (4) lysozyme (5) Q-chymotrypsin (6) a-chymotrypsinogen.

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