Investigation of the malE Promoter and MalR, a Positive Regulator of the Maltose Regulon, for an Improved Expression System in Sulfolobus acidocaldarius

In this study, the regulator MalR (Saci_1161) of the TrmB family from Sulfolobus acidocaldarius was identified and was shown to be involved in transcriptional control of the maltose regulon (Saci_1660 to Saci_1666), including the ABC transporter (malEFGK), alpha-amylase (amyA), and alpha-glycosidase (malA). The Delta malR deletion mutant exhibited a significantly decreased growth rate on maltose and dextrin but not on sucrose. The expression of the genes organized in the maltose regulon was induced only in the presence of MalR and maltose in the growth medium, indicating that MalR, in contrast to its TrmB and TrmB-like homologues, is an activator of the maltose gene cluster. Electrophoretic mobility shift assays revealed that the binding of MalR to malE was independent of sugars. Here we report the identification of the archaeal maltose regulator protein MalR, which acts as an activator and controls the expression of genes involved in maltose transport and metabolic conversion in S. acidocaldarius, and its use for improvement of the S. acidocaldarius expression system under the control of an optimized maltose binding protein (malE) promoter by promoter mutagenesis.