Results
Cel9B truncation mutants were designed in such a way that five different structural domains (identified in the CAZy website; (http://www.cazy.org/) Lombard et al., 2013) were either removed or retained with the objective of elucidating their specific function (Figure 1, Table 2). All the truncation mutants contained a His tag so that they could be easily purified on a nickel column. Although each of the seven mutants tested exhibited activity on CMC, it was observed that mutant Fn3, which retained the fibronectin-like domain located within the protein, had a reduced capacity to bind to the nickel column. This suggested that the protein structure had been altered so that the 6His tag was no longer available to bind to the column. In addition to this, the truncation mutant ΔFn39B grew poorly.