The 2 S seed storage protein, sunflower albumin 8 (SFA-8), contains an unusually high proportion of hydrophobic residues including 16 methionines (some of which may form a surface hydrophobic patch) in a disulfide cross-linked, alpha-helical structure. Circular dichroism and fluorescence spectroscopy show that SFA-8 is highly stable to denaturation by heating or chaotropic agents, the latter resulting in a reversible two-state unfolding transition. The small m(U) (-4.7 M(-1) at 10 degrees C) and DeltaC(p) (-0.95 kcal mol(-1) K(-1)) values indicate that relatively little nonpolar surface of the protein is exposed during unfolding. Commensurate with the unusual distribution of hydrophobic residues, stopped-flow fluorescence data show that the folding pathway of SFA-8 is highly atypical, in that the initial product of the rapid collapse phase of folding is a compact nonnative state (or collection of nonnative states) that must unfold before acquiring the native conformation. The inhibited folding reaction of SFA-8, in which the misfolded state (m(M) = -0.95 M(-1) at 10 degrees C) is more compact than the transition state for folding (m(T) = -2.5 M(-1) at 10 degrees C), provides direct kinetic evidence for the transient misfolding of a protein. Study holds ProTherm entries: 6375, 6376 Extra Details: methionine; surface hydrophobic patch; alpha-helical structure;,folding pathway; transition state
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:31 p.m.
|Number of data points||7|
|Proteins||2S seed storage protein|
|Assays/Quantities/Protocols||Experimental Assay: dCp temp:25.0 C ; Experimental Assay: dG_H2O temp:25.0 C ; Experimental Assay: dHvH temp:25.0 C ; Experimental Assay: dCp temp:10.0 C ; Experimental Assay: dG_H2O temp:10.0 C ; Experimental Assay: m ; Experimental Assay: dHvH temp:10.0 C|
|Libraries||Mutations for sequence MAKQIVLALAFAALVAFATAHTTIITTTIEDENPISGQRQVSQRIQGQRLNQCRMFLQQGQNIPREFDNPQMGRQQEQQLQQCCQELQNIEGQCQCEAVKQVFREAQQQVQQQQGRQLVPFRGSQQTQQLKQKAQILPNVCNLQSRRCEIGTITTTVTESNIDIPFRDRPFGTGSQQCRETEIQRPVGECQRFVEQQMQQSPRSTRPYQQRPGQQQQQQRGLQQQCCNELQNVKRECHCEAIQEVARRVMRQPQQQQQQRRGQFGGQEMETARRVIQNLPNQCDLEVQQCTTCTG|