Protein expression profiles of different ArgT expression strains at 37°C. Proteins were separated by IEF in the first dimension (18 cm) with the pI range of pH 4-7 and pH6-11 and by 12.5% SDS-PAGE in the second dimension and then stained by Coomassie. HtrA presents two spots in the expression profile of 2457T. The abundance of the left is higher than the right in the wild type, while the abundance of the right is higher than the left in argT deletion mutant. Only the left can be detected in the ArgT over-expression strain.