NMR Study of the Structures of Repeated Sequences, GAGXGA (X = S, Y, V), in Bombyx mori Liquid Silk

摘要

The silk fibroin stored in the silk gland of the Bombyx mori silkworm, called "liquid silk", is spun out and converted into the silk fiber with extremely high strength and high toughness. Therefore it is important to determine the silk structure before spinning called Silk 1 at an atomic level to clarify the fiber formation mechanism. We proposed the repeated type II.β-tum structure as Silk I in the solid state with the model peptide (AG)_(15) and several solid state NMR techniques previously. In this paper, the solution structure of native "liquid silk" was determined with solution NMR, especially for tandem repeated sequences with (GAGXGA)_n (X = S, Y, V) and GAASGA motifs in the B. mori silk fibroin. The assignment of the ~(13)C, ~(15)N, and ~1H solution NMR spectra for the repetitive sequence motifs was achieved, and the chemical shifts were obtained.