Electrostatics analysis of the mutational and pH effects of the N-terminal domain self-association of the major ampullate spidroin

Author(s)

Barroso da Silva, Fernando Luis ^{[1, 2, 3]} ; Pasquali, Samuela ^{[1, 2]} ; Derreumaux, Philippe ^{[1, 2, 4]} ; Dias, Luis Gustavo ^[5]

Affiliation

^[1] Univ Paris 07, Inst Biol Physico Chim, CNRS, Lab Biochim Theor, UPR 9080, 13 Rue Pierre & Marie Curie, F-75005 Paris - France

^[2] Univ Sorbonne Paris Cite, 13 Rue Pierre & Marie Curie, F-75005 Paris - France

^[3] Univ Sao Paulo, Fac Ciencias Farmaceut Ribeirao Preto, Dept Fis & Quim, Ave Cafe S-No, BR-14040903 Ribeirao Preto, SP - Brazil

^[4] Inst Univ France, 103 Blvd St Michel, F-75005 Paris - France

^[5] Univ Sao Paulo, Dept Quim, Fac Filosofia Ciencias & Letras Ribeirao Preto, Ave Bandeirantes 3900, BR-14040903 Ribeirao Preto, SP - Brazil

• Document type: Journal article
• Source: SOFT MATTER; v. 12, n. 25, p. 5600-5612, 2016.
• Web of Science Citations: 10

Abstract

Spider silk is a fascinating material combining mechanical properties such as maximum strength and high toughness comparable or better than man-made materials, with biocompatible degradability characteristics. Experimental measurements have shown that pH triggers the dimer formation of the N-terminal domain (NTD) of the major ampullate spidroin 1 (MaSp 1). A coarse-grained model accounting for electrostatics, van der Waals and pH-dependent charge-fluctuation interactions, by means of Monte Carlo simulations, gave us a more comprehensive view of the NTD dimerization process. A detailed analysis of the electrostatic properties and free energy derivatives for the NTD homoassociation was carried out at different pH values and salt concentrations for the protein wild type and for several mutants. We observed an enhancement of dipole-dipole interactions at pH 6 due to the ionization of key amino acids, a process identified as the main driving force for dimerization. Analytical estimates based on the DVLO theory framework corroborate our findings. Molecular dynamics simulations using the OPEP coarse-grained force field for proteins show that the mutant E17Q is subject to larger structural fluctuations when compared to the wild type. Estimates of the association rate constants for this mutant were evaluated by the Debye-Smoluchowski theory and are in agreement with the experimental data when thermally relaxed structures are used instead of the crystallographic data. Our results can contribute to the design of new mutants with specific association properties. (AU)

• FAPESP's process: 13/08166-5 - Interfacial chemistry: drugs, peptides and ezymes interactions with membrane models
• Grantee: Iolanda Midea Cuccovia
• Support Opportunities: Research Projects - Thematic Grants