A comparison of folding techniques in the chemical synthesis of the epidermal growth factor-like domain in neu differentiation factor alpha/beta.
The 52-residue alpha/beta chimera of the epidermal growth factor-like domain in neu differentiation factor (NDFealpha/beta) has been synthesized and folded to form a three disulfide bridge (Cys182-Cys196, Cys190-Cys210, Cys212-Cys221) containing peptide. We investigated two general strategies for the formation of the intramolecular disulfide bridges including, the single-step approach, which used fully deprotected and reduced peptide, and a sequential approach that relied on orthogonal cysteine protection in which specific pairs are excluded from the first oxidation step. Because there are 15 possible disulfide bridge arrangements in a peptide with six cysteines, the one-step approach may not always provide the desired disulfide pairing. Here, we compare the single-step approach with a systematic evaluation of the sequential approach. We employed the acetamidomethyl group to protect each pair of cysteines involved in disulfide bridges, i.e. Cys182 to Cys196, Cys190 to Cys210 and Cys212 to Cys221. This reduced the number of possible disulfide patterns from 15 to three in the first folding step. We compared the efficiencies of folding for each protected pair using RP-HPLC, mapped the disulfide connectivity of the predominant product and then formed the final disulfide from the partially folded intermediate via 12 oxidation. Only the peptide having the Cys182-Cys196 pair blocked with acetamidomethyl forms the desired disulfide isomer (Cys190-Cys210/Cys212-Cys221) as a single homogeneous product. By optimizing both approaches, as well as other steps in the synthesis, we can now rapidly provide large-scale syntheses of NDFealpha/beta and other novel EGF-like peptides.
Zamborelli
T J
TJ
Amgen Inc., Boulder, CO 80301, USA.
Dodson
W S
WS
Harding
B J
BJ
Zhang
J
J
Bennett
B D
BD
Lenz
D M
DM
Young
Y
Y
Haniu
M
M
Liu
C F
CF
Jones
T
T
Jarosinski
M A
MA
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D003545:Cysteine / Q000737:chemistry; D004220:Disulfides; D004815:Epidermal Growth Factor / Q000737:chemistry*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D020890:Neuregulin-1 / Q000138:chemical synthesis / Q000737:chemistry*; D010452:Peptide Biosynthesis; D010455:Peptides / Q000737:chemistry; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013997:Time Factors
D000596:Amino Acids; D004220:Disulfides; D020890:Neuregulin-1; D010455:Peptides; D004815:Epidermal Growth Factor; D003545:Cysteine