A peptide derived from the C‐terminal part of a plant cysteine protease folds into a stack of two β‐hairpins, a scaffold present in the emerging family of granulin‐like growth factors

Abstract

A 35 amino acid residue peptide corresponding to the N-terminal subdomain of the granulin-like repeat from rice oryzain beta was synthesized and regioselectively oxidized to produce a species with a [1-3, 2-4] disulfide-pairing pattern. The resulting peptide was studied in solution using NMR and was shown to adopt the tertiary topology of a stack of two beta-hairpins found in the emerging family of granulin-like growth factors. Because of the longer second beta-hairpin, the overall conformation of the peptide is somewhat more flexible than that of its well-structured carp granulin-1 analog. Except for the cysteine alignment, there is very little sequence homology between granulin-like growth factors from the animal kingdom and the granulin-like repeats at the C-termini of plant cysteine proteases. Therefore, the stack of two beta-hairpins may be a conserved three-dimensional organization of the granulin-like repeats from evolutionary distant sources with a significant role in specific protein-protein interactions.