title: Local structural preferences in the alpha-lactalbumin molten globule.
abstract: Molten globules have been proposed to be general intermediates in protein folding. Despite numerous studies, a detailed description of the structure of a molten globule remains elusive. Recently, we showed that the molten globule formed by the helical domain of alpha-lactalbumin (alpha-LA) has a native-like backbone topology. Here we probe local structural preferences in the helical domain of the alpha-LA molten globule by analyzing a set of native and nonnative single disulfide bond variants using a combination of circular dichroism spectroscopy and determination of the equilibrium constant for disulfide bond formation. We find that the region surrounding the 28-111 disulfide bond has a high preference to adopt a native-like structure. Formation of other native or nonnative disulfide bonds is significantly less favorable. Our results suggest that molten globules contain regions with varying degrees of specificity for native-like structure and that the core region surrounding the 28-111 disulfide bond plays an important role in alpha-LA folding by stabilizing the molten globule intermediate.
authors.affiliation: Howard Hughes Medical Institute, Whitehead Institute for Biomedical Research, Department of Biology, Massachusetts Institute of Technology, Nine Cambridge Center 02142.
authors.forename: Z Y
authors.initials: ZY
authors.lastname: Peng
authors.forename: L C
authors.initials: LC
authors.lastname: Wu
authors.forename: P S
authors.initials: PS
authors.lastname: Kim
mesh_terms: D002942:Circular Dichroism; D003001:Cloning, Molecular; D004220:Disulfides / Q000737:chemistry; D004926:Escherichia coli / Q000235:genetics; D006801:Humans; D007768:Lactalbumin / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D015394:Molecular Structure; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
chemical_list: D004220:Disulfides; D007768:Lactalbumin