What is a "Kozak Consensus Sequence"?

The Kozak consensus sequence was originally defined as ACCAUGG following an analysis of the effects of single mutations surrounding the initiation codon (AUG) on translation of the preproinsulin gene . Subsequent mutagenesis studies and a survey of 699 vertebrate mRNAs extended the consensus sequence for translation initiation to GCCGCCACCAUGG, where the A in the underlined AUG start codon is coordinate 1 and the A at position –3 could also be a G . Functional studies on preproinsulin and alpha-globin translation in cells indicated that a purine (usually A) in position –3 is crucial for efficient initiation of translation, and in its absence, a G at position +4 is essential . RNA templates with CCACCAUGG were translated well in a study using the Rabbit Reticulocyte Lysate System (Cat.# L4960) in vitro translation reaction . In the in vitro translation reaction using the TnT® T7 Quick Coupled Transcription/Translation System (Cat.# L1170, L1171, L5540), PCR products can be used as templates . The upstream primer for generating the PCR template was designed to contain the T7 promoter for transcription by T7 RNA Polymerase (Cat.# P2075) and the Kozak consensus sequence (CCACCAUG or CCACCAUGG) for efficient translation .