The native state (1)H, (15)N resonance assignment of 123 of the 128 nonproline residues of canine milk lysozyme has enabled measurements of the amide hydrogen exchange of over 70 amide hydrogens in the molten globule state. To elucidate the mechanism of protein folding, the molten globule state has been studied as a model of the folding intermediate state. Lysozyme and alpha-lactalbumin are homologous to each other, but their equilibrium unfolding mechanisms differ. Generally, the folding mechanism of lysozyme obeys a two-state model, whereas that of alpha-lactalbumin follows a three-state model. Exceptions to this rule are equine and canine milk lysozymes, which exhibit a partially unfolded state during the equilibrium unfolding; this state resembles the molten globule state of alpha-lactalbumin but with extreme stability. Study of the molten globules of alpha-lactalbumin and equine milk lysozyme showed that the stabilities of their alpha-helices are similar, despite the differences in the thermodynamic stability of their molten globule states. On the other hand, our hydrogen exchange study of the molten globule of canine milk lysozyme showed that the alpha-helices are more stabilized than in alpha-lactalbumin or equine milk lysozyme and that this enhanced stability is caused by the strengthened cooperative interaction between secondary structure elements. Thus, our results underscore the importance of the cooperative interaction in the stability of the molten globule state. Study holds ProTherm entries: 8507, 8508, 8509, 8510 Extra Details: additive : EDTA(1 mM),N->I; apo form alpha-lactalbumin; Ca2+-binding lysozyme; cooperativity;,folding; NMR; stability; unfolding
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:36 p.m.
|Number of data points||8|
|Proteins||Lysozyme C, milk isozyme ; Lysozyme C, milk isozyme|
|Assays/Quantities/Protocols||Experimental Assay: m ionic:CaCl2: 2 mM ; Experimental Assay: dG_H2O ionic:CaCl2: 2 mM ; Experimental Assay: m ionic:: ; Experimental Assay: dG_H2O ionic::|
|Libraries||Mutations for sequence SKIFSKCELARKLKSMGMDGFHGYSLANWVCMAEYESNFNTQAFNGRNSNGSSDYGIFQLNSKWWCKSNSHSSANACNIMCSKFLDDNIDDDIACAKRVVKDPNGMSAWVAWVKHCKGKDLSKYLASCNL|