Activates transcription. Positively regulates six promoters upstream of the TTHB186, TTHB147, TTHB178, TTHB159, TTHA0771 and TTHA0176 genes in a cAMP-dependent manner. Regulated genes include clustered regularly interspaced short palindromic repeat (CRISPR) associated (Cas) genes, and the genes encoding a putative transcriptional regulator, a protein containing the exonuclease III-like domain of DNA polymerase, a GCN5-related acetyltransferase homolog, and some T.thermophilus-specific proteins of unknown function. The consensus DNA-binding site of this transcriptional regulator is 5'-(CT)NNG(G/T)(G/T)C(A/C)N(A/T)NNTCACAN(G/C)(G/C)-3' in which N is G, A, T or C. Homodimer. Decreased expression of genes downstream of the TTHB186, TTHB147 and TTHB159 genes. Decreased expression of TTHB178, TTHA0771 and TTHA0176 genes.