The Kozak sequence directs the pre-initiation complex (PIC) and ribosome to the translation initiation site (start codon) and mediates ribosome assembly ensuring the correct protein sequence is translated.

The consensus Kozak sequence is generally considered as GCCGCCACCATGG, where ATG is the start codon (typically the start of the signal sequence). Twist recommends the version GCCGCCACC upstream of the start codon ATG.