Mutation of the Flo1 flocculation protein for enhancing the oligomannose
AbstractYeast cell flocculation is a common cellular adhesion process which
increases the efficiency of yeast cell harvest and recovery in the beer
industry and biofuel production. The flocculation involves the binding
of exopolysaccharides to the flocculation protein of neighboring cell.
It is of great interest to examine the roles of key amino acid residues
in modulating polysaccharide binding which regulates the flocculation.
In this work, proper mutation sites were identified via alanine scanning
mutagenesis incorporated with molecular dynamics simulations of
protein-mannobiose complexes based on the crystal structure of
flocculation protein Flo1p. Two mutants Q117N and Q117R have been
selected out of nine examined mutants, with stronger binding free
energies for the mannobiose binding, comparing to the wild type protein.
The two mutants also show enhanced binding in the protein-mannotriose
complexes which consist of three mannose residues, fulfilling the
capacity of the binding site, and can be used to evaluate the binding
strength of oligomannose. Hydrogen bonding, conformational stability and
shape change were analyzed to help understand the protein-mannotriose
interactions. This study also shows a way to alternate oligosaccharide
binding to proteins functioning in other biological processes.