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Independent of their localization in protein the hydrophobic amino acid residues have no effect on the molten globule state of apomyoglobin and the disulfide bond on the surface of apomyoglobin stabilizes this intermediate state.

Melnik TN, Majorina MA, Larina DS, Kashparov IA, Samatova EN, Glukhov AS, Melnik BS - PLoS ONE (2014)

Bottom Line: In this study, we have investigated the effect of substitutions of hydrophobic amino acid residues in the hydrophobic core of protein and on its surface on a molten globule type intermediate state of apomyoglobin.It has been found that independent of their localization in protein, substitutions of hydrophobic amino acid residues do not affect the stability of the molten globule state of apomyoglobin.The result obtained allows us not only to conclude which mutations can have an effect on the intermediate state of the molten globule type, but also explains why the introduction of a disulfide bond (which seems to "strengthen" the protein) can result in destabilization of the protein native state of apomyoglobin.

View Article: PubMed Central - PubMed

Affiliation: Institute of Protein Research, RAS, Pushchino, Moscow Region, Russia.

ABSTRACT
At present it is unclear which interactions in proteins reveal the presence of intermediate states, their stability and formation rate. In this study, we have investigated the effect of substitutions of hydrophobic amino acid residues in the hydrophobic core of protein and on its surface on a molten globule type intermediate state of apomyoglobin. It has been found that independent of their localization in protein, substitutions of hydrophobic amino acid residues do not affect the stability of the molten globule state of apomyoglobin. It has been shown also that introduction of a disulfide bond on the protein surface can stabilize the molten globule state. However in the case of apomyoglobin, stabilization of the intermediate state leads to relative destabilization of the native state of apomyoglobin. The result obtained allows us not only to conclude which mutations can have an effect on the intermediate state of the molten globule type, but also explains why the introduction of a disulfide bond (which seems to "strengthen" the protein) can result in destabilization of the protein native state of apomyoglobin.

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Effect of the SS-bond on apomyoglobin molten globule state stability.(A) Ribbon model of myoglobin. Letters A through H denote α-helices. Amino acid residues His36 and Phe106 replaced by cysteine residues are shown three-dimensionally. α-Helices that are the first to fold (see the text) are shown in red color. (B) Dependency of the population fI of the molten globule state versus urea concentration for apomyoglobin (○), its mutant form with SS-bond between amino acids 36 and 106 (•) and the protein mutant form with cysteine residues modified by iodoacetamide (▪).
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pone-0098645-g005: Effect of the SS-bond on apomyoglobin molten globule state stability.(A) Ribbon model of myoglobin. Letters A through H denote α-helices. Amino acid residues His36 and Phe106 replaced by cysteine residues are shown three-dimensionally. α-Helices that are the first to fold (see the text) are shown in red color. (B) Dependency of the population fI of the molten globule state versus urea concentration for apomyoglobin (○), its mutant form with SS-bond between amino acids 36 and 106 (•) and the protein mutant form with cysteine residues modified by iodoacetamide (▪).

Mentions: To simulate an SS-bond in apomyoglobin it is necessary to take into account several facts. Myoglobin has been crystallized only in a holo-form (with the heme). In apomyoglobin, α-helix F (see Fig. 5) is unfolded [56]. It is known from the NMR studies that α-helices A, B, G, and H are formed at the earliest stages of apomyoglobin folding [56]. Based on all this, in order to introduce SS-bond we have searched for amino acid residues neighboring on the surface of myoglobin located on α-helices A, B, G, and H. We have chosen His36 and Phe106. The distance and mutual orientation of these amino acid residues are appropriate for the formation of an SS-bond when they are substituted by cysteine residues.


Independent of their localization in protein the hydrophobic amino acid residues have no effect on the molten globule state of apomyoglobin and the disulfide bond on the surface of apomyoglobin stabilizes this intermediate state.

Melnik TN, Majorina MA, Larina DS, Kashparov IA, Samatova EN, Glukhov AS, Melnik BS - PLoS ONE (2014)

Effect of the SS-bond on apomyoglobin molten globule state stability.(A) Ribbon model of myoglobin. Letters A through H denote α-helices. Amino acid residues His36 and Phe106 replaced by cysteine residues are shown three-dimensionally. α-Helices that are the first to fold (see the text) are shown in red color. (B) Dependency of the population fI of the molten globule state versus urea concentration for apomyoglobin (○), its mutant form with SS-bond between amino acids 36 and 106 (•) and the protein mutant form with cysteine residues modified by iodoacetamide (▪).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4043776&req=5

pone-0098645-g005: Effect of the SS-bond on apomyoglobin molten globule state stability.(A) Ribbon model of myoglobin. Letters A through H denote α-helices. Amino acid residues His36 and Phe106 replaced by cysteine residues are shown three-dimensionally. α-Helices that are the first to fold (see the text) are shown in red color. (B) Dependency of the population fI of the molten globule state versus urea concentration for apomyoglobin (○), its mutant form with SS-bond between amino acids 36 and 106 (•) and the protein mutant form with cysteine residues modified by iodoacetamide (▪).
Mentions: To simulate an SS-bond in apomyoglobin it is necessary to take into account several facts. Myoglobin has been crystallized only in a holo-form (with the heme). In apomyoglobin, α-helix F (see Fig. 5) is unfolded [56]. It is known from the NMR studies that α-helices A, B, G, and H are formed at the earliest stages of apomyoglobin folding [56]. Based on all this, in order to introduce SS-bond we have searched for amino acid residues neighboring on the surface of myoglobin located on α-helices A, B, G, and H. We have chosen His36 and Phe106. The distance and mutual orientation of these amino acid residues are appropriate for the formation of an SS-bond when they are substituted by cysteine residues.

Bottom Line: In this study, we have investigated the effect of substitutions of hydrophobic amino acid residues in the hydrophobic core of protein and on its surface on a molten globule type intermediate state of apomyoglobin.It has been found that independent of their localization in protein, substitutions of hydrophobic amino acid residues do not affect the stability of the molten globule state of apomyoglobin.The result obtained allows us not only to conclude which mutations can have an effect on the intermediate state of the molten globule type, but also explains why the introduction of a disulfide bond (which seems to "strengthen" the protein) can result in destabilization of the protein native state of apomyoglobin.

View Article: PubMed Central - PubMed

Affiliation: Institute of Protein Research, RAS, Pushchino, Moscow Region, Russia.

ABSTRACT
At present it is unclear which interactions in proteins reveal the presence of intermediate states, their stability and formation rate. In this study, we have investigated the effect of substitutions of hydrophobic amino acid residues in the hydrophobic core of protein and on its surface on a molten globule type intermediate state of apomyoglobin. It has been found that independent of their localization in protein, substitutions of hydrophobic amino acid residues do not affect the stability of the molten globule state of apomyoglobin. It has been shown also that introduction of a disulfide bond on the protein surface can stabilize the molten globule state. However in the case of apomyoglobin, stabilization of the intermediate state leads to relative destabilization of the native state of apomyoglobin. The result obtained allows us not only to conclude which mutations can have an effect on the intermediate state of the molten globule type, but also explains why the introduction of a disulfide bond (which seems to "strengthen" the protein) can result in destabilization of the protein native state of apomyoglobin.

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