Loosenin, a novel protein with cellulose-disrupting activity from Bjerkandera adusta

Rosa E Quiroz-Castañeda,Lorenzo Segovia,Claudia Martínez-Anaya,Jorge L Folch-Mallol,Laura I Cuervo-Soto

doi:10.1186/1475-2859-10-8

Abstract

BackgroundExpansins and expansin-like proteins loosen cellulose microfibrils, possibly through the rupture of intramolecular hydrogen bonds. Together with the use of lignocellulolytic enzymes, these proteins are potential molecular tools to treat plant biomass to improve saccharification yields.ResultsHere we describe a new type of expansin-related fungal protein that we have called loosenin. Its corresponding gene, loos1, from the basidiomycete Bjerkandera adusta, was cloned and heterologously expressed in Saccharomyces cerevisiae. LOOS1 is distantly related to plant expansins through the shared presence of a DPBB domain, however domain II found in plant expansins is absent. LOOS1 binds tightly to cellulose and chitin, and we demonstrate that cotton fibers become susceptible to the action of a commercial cellulase following treatment with LOOS1. Natural fibers of Agave tequilana also become susceptible to hydrolysis by cellulases after loosenin treatment.ConclusionsLOOS1 is a new type of protein with disrupting activity on cellulose. LOOS1 binds polysaccharides, and given its enhancing properties on the action of hydrolytic enzymes, LOOS1 represents a potential additive in the production of fermentable sugars from lignocellulose.

Highlights

Expansins and expansin-like proteins loosen cellulose microfibrils, possibly through the rupture of intramolecular hydrogen bonds
Bjerkandera adusta is a basidiomycete fungus well known for its high ligninase activity [3] and recently, its cellulolytic capabilities have been characterized [4,5]
We aimed to determine if loos1 was expressed under lignocellulose growing conditions. cDNA was amplified by RT-PCR from total RNA, obtained from B. adusta grown on wheat straw medium

Summary

Introduction

Expansins and expansin-like proteins loosen cellulose microfibrils, possibly through the rupture of intramolecular hydrogen bonds. Together with the use of lignocellulolytic enzymes, these proteins are potential molecular tools to treat plant biomass to improve saccharification yields. Filamentous fungi, especially white-rot type basidiomycetes, efficiently degrade plant cell wall biopolymers due to the production of a battery of extracellular enzymes such as cellulases, hemicellulases and ligninases [2]. Basidiomycete fungi represent a source of enzymes with potential applications due to their elevated ligninolytic activity. Plant cell walls are physiologically remodeled by a group of proteins with the ability to relax their components and promote cell enlargement [6].

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