Download MendeleyUnusual p K a Values Mediate the Self-Assembly of Spider Dragline Silk Proteins.
Oktaviani, N.A., Malay, A.D., Matsugami, A., Hayashi, F., Numata, K.(2023) Biomacromolecules 24: 1604-1616
- PubMed: 36990448
- DOI: https://doi.org/10.1021/acs.biomac.2c01344
- Primary Citation of Related Structures:
7WIO, 8GS7 - PubMed Abstract:
Spider dragline silk is a remarkably tough biomaterial and composed primarily of spidroins MaSp1 and MaSp2. During fiber self-assembly, the spidroin N-terminal domains (NTDs) undergo rapid dimerization in response to a pH gradient. However, obtaining a detailed understanding of this mechanism has been hampered by a lack of direct evidence regarding the protonation states of key ionic residues. Here, we elucidated the solution structures of MaSp1 and MaSp2 NTDs from Trichonephila clavipes and determined the experimental p K a values of conserved residues involved in dimerization using NMR. Surprisingly, we found that the Asp40 located on an acidic cluster protonates at an unusually high pH (∼6.5-7.1), suggesting the first step in the pH response. Then, protonation of Glu119 and Glu79 follows, with p K a s above their intrinsic values, contributing toward stable dimer formation. We propose that exploiting the atypical p K a values is a strategy to achieve tight spatiotemporal control of spider silk self-assembly.
Organizational Affiliation:
Biomacromolecules Research Team, RIKEN Center for the Sustainable Resource Sciences, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
