Journal
NATURE COMMUNICATIONS
Volume 9, Issue -, Pages -Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/s41467-018-06362-3
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Funding
- Ministry of Education, Culture, Sports, Science, and Technology (MEXT), Japan [JP17K19213, JP16H00789, JP16H00858, JP15H04366, JP15H06898, JP17K18429, JP17H05899]
- Advanced Technology Institute Research Grants [RG2709]
- National Institutes of Natural Sciences (NINS) [01311805]
- Building of Consortia for the Development of Human Resources in Science and Technology, MEXT, Japan
- [JP18H05424]
- [J281002]
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Processive chitinase is a linear molecular motor which moves on the surface of crystalline chitin driven by processive hydrolysis of single chitin chain. Here, we analyse the mechanism underlying unidirectional movement of Serratia marcescens chitinase A (SmChiA) using high-precision single-molecule imaging, X-ray crystallography, and all-atom molecular dynamics simulation. SmChiA shows fast unidirectional movement of similar to 50 nm s(-1) with 1 nm forward and backward steps, consistent with the length of reaction product chitobiose. Analysis of the kinetic isotope effect reveals fast substrate-assisted catalysis with time constant of similar to 3 ms. Decrystallization of the single chitin chain from crystal surface is the rate-limiting step of movement with time constant of similar to 17 ms, achieved by binding free energy at the product-binding site of SmChiA. Our results demonstrate that SmChiA operates as a burnt-bridge Brownian ratchet wherein the Brownian motion along the single chitin chain is rectified forward by substrate-assisted catalysis.
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