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The heat shock response is an evolutionarily conserved, stress-responsive signaling pathway that adapts cellular proteostasis in response to pathologic insult. In metazoans, the heat shock response primarily functions through the posttranslational activation of heat shock factor 1 (HSF1), a stress-responsive transcription factor that induces the expression(More)
Collagen is the most abundant protein in animals. This fibrous, structural protein comprises a right-handed bundle of three parallel, left-handed polyproline II-type helices. Much progress has been made in elucidating the structure of collagen triple helices and the physicochemical basis for their stability. New evidence demonstrates that stereoelectronic(More)
In previous work, we demonstrated that 4-fluoroproline residues can contribute greatly to the conformational stability of the collagen triple helix, and that this stability arises from stereoelectronic effects that fix the pucker of the pyrrolidine ring and thereby preorganize the backbone properly for triple-helix formation. Here, we take a reciprocal(More)
Preorganization is shown to endow a protein with extraordinary conformational stability. This preorganization is achieved by installing side-chain substituents that impose stereoelectronic and steric effects that restrict main-chain torsion angles. Replacing proline residues in (ProProGly)(7) collagen strands with 4-fluoroproline and 4-methylproline leads(More)
According to a prevailing theory, (2S,4R)-4-hydroxyproline (Hyp) residues stabilize the collagen triple helix via a stereoelectronic effect that preorganizes appropriate backbone torsion angles for triple-helix formation. This theory is consistent with the marked stability that results from replacing the hydroxyl group with the more electron-withdrawing(More)
Collagen is an abundant, triple-helical protein comprising three strands of the repeating sequence: Xaa-Yaa-Gly. (2S)-Proline and (2S,4R)-4-hydroxyproline (Hyp) are common in the primary structure of collagen. Here, we use nonnatural proline derivatives to reveal determinants of collagen stability. Specifically, we report high-yielding syntheses of(More)
The amino acid sequence of collagen is composed of GlyXaaYaa repeats. A prevailing paradigm maintains that stable collagen triple helices form when (2S)-proline (Pro) or Pro derivatives that prefer the C(γ)-endo ring pucker are in the Xaa position and Pro derivatives that prefer the C(γ)-exo ring pucker are in the Yaa position. Anomalously, an amino acid(More)
Prolyl 4-hydroxylases install a hydroxyl group in the 4R configuration on the gamma-carbon atom of certain (2S)-proline (Pro) residues in tropocollagen, elastin, and other proteins to form (2S,4R)-4-hydroxyproline (Hyp). The gauche effect arising from this prevalent post-translational modification enforces a C(gamma)-exo ring pucker and stabilizes the(More)
N-acetylmethanopyrrolidine methyl ester and its four 5-syn/anti-fluoro and hydroxy derivatives have been synthesized from 2-azabicyclo[2.2.0]hex-5-ene, a 1,2-dihydropyridine photoproduct. These conformationally constrained mimics of idealized C(β)-gauche and C(β)-anti conformers of pyrrolidines were prepared in order to determine the inherent bridge bias(More)