TTATNCACA

TTATNCACA is a consensus DNA sequence motif found in many bacterial origins of replication, notably within the oriC region of Escherichia coli. The notation indicates a nine-nucleotide sequence where the letter N represents any nucleotide, giving the core pattern T T A T N C A C A. This motif is known as a DnaA box and serves as a binding site for the initiator protein DnaA, which is essential for starting chromosomal replication.

In the bacterial initiation process, DnaA binds to multiple TTATNCACA sites within oriC, often in cooperation with ATP binding. The assembly of DnaA at these boxes helps recruit and organize other replication proteins, including the helicase loader complex, and promotes local unwinding of the adjacent DNA unwinding element. This series of events facilitates the loading of the helicase and the progression to bidirectional replication.

The TTATNCACA motif is conserved in many bacterial species but occurs in varying numbers and arrangements across different genomes. Its presence and integrity are important for proper initiation; mutations or deletions within core DnaA boxes can impair origin opening and slow or prevent replication initiation. Because of its central role, TTATNCACA and related DnaA boxes are frequently used in comparative genomics and genome annotation to identify potential origins of replication in bacterial genomes.

See also: DnaA box, oriC, DNA replication initiation.