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Formation of a native‐like subdomain in a partially folded intermediate of bovine pancreatic trypsin inhibitor
Author(s) -
Staley Jonathan P.,
Kim Peter S.
Publication year - 1994
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.5560031021
Subject(s) - chemistry , protein folding , folding (dsp implementation) , crystallography , peptide , trypsin , stereochemistry , protein tertiary structure , recombinant dna , protein structure , biochemistry , enzyme , electrical engineering , engineering , gene
In the folding of bovine pancreatic trypsin inhibitor (BPTI), the single‐disulfide intermediate [30–51] plays a key role. We have investigated a recombinant analog of [30–51] using 2‐dimensional nuclear magnetic resonance (2D‐NMR). This recombinant analog, named [30–51] Ala , contains a disulfide bond between Cys‐30 and Cys‐51, but contains alanine in place of the other cysteines in BPTI to prevent the formation of other intermediates. By 2D‐NMR, [30–51] Ala consists of 2 regions —one folded and one predominantly unfolded. The folded region resembles a previously characterized peptide model of [30–51], named PαPβ, that contains a native‐like subdomain with tertiary packing. The unfolded region includes the first 14 N‐terminal residues of [30–51] and is as unfolded as an isolated peptide containing these residues. Using protein dissection, we demonstrate that the folded and unfolded regions of [30–51] Ala are structurally independent. The partially folded structure of [30–51] Ala explains many of the properties of authentic [30–51] in the folding pathway of BPTI. Moreover, direct structural characterization of [30–51] Ala has revealed that a crucial step in the folding pathway of BPTI coincides with the formation of a native‐like subdomain, supporting models for protein folding that emphasize the formation of cooperatively folded subdomains.