The correlation between protein structure and function is well established, yet the role stability/flexibility plays in protein function is being explored. Here, we describe an in vivo screen in which the thermal stability of a test protein is correlated directly to the transcriptional regulation of a reporter gene. The screen readout is independent of the function of the test protein, proteolytic resistance, solubility or propensity to aggregate indiscrimi- nately, and is thus dependent solely on the overall stability of the test protein. The system entails the use of an engineered chimeric construct that consists of three covalently linked domains; a constant N-terminal DNA- binding domain, a variable central test protein, and a constant C-terminal transcriptional activation domain. The test proteins are mutant variants of the β1 domain of streptococcal protein G that span fairly evenly a thermal stability range from as low as 38 °C to above 100 °C. When the chimeric construct contains a test variant of low thermal stability, the reporter gene is up-regulated to a greater extent relative to that of more stable/less flexible variants. A panel of nine Gβ1 mutant variants was used to benchmark the screen, and spectroscopic methods were employed to characterize the thermal and structural properties of each variant accurately. The screen was combined with in silico methods to interrogate a library of randomized variants for selection of mutants of greater structural integrity.
Submitter: Marie Ary
Submission Date: July 31, 2017, 11:46 a.m.
|Number of data points||55|
|Assays/Quantities/Protocols||Experimental Assay: Tm ; Experimental Assay: in vitro proteolysis ; Experimental Assay: Bacterial growth in 3000 ug/ml carbenicillin (antibiotic)|
|Libraries||random mutagenesis (#1-5) and CPD of MonB (MonB-ORDES) at pos 23, 27, 45 to validate utility of chimeric screen (Table 3 Tm and OD) ; GB1 mutants with variable stability for use in testing in vivo chimeric screen (Table 1 Tm + Fig 4 OD + Table 2 Proteolysis)|