Depending on the presence of the two critical bases -3R and +4G, TIS contexts were classified as Kozak motifs that are “optimal”, GCCRCCAUGG (only for vertebrates); “strong”, RNNAUGG (the two key bases are present; N, any base); “moderate”, RNNAUGH or YNNAUGG (only one of the key nucleotides is present; Y, C/U; H, A/C/U); “weak”, YNNAUGH.
Ref: PMID: 12459250; PMID: 31353284.
A novel category of eight sequences that significantly disfavor mRNA translation, termed “barren AUG context sequences” (BACS) has been described: these are CCAAUGU, UUAAUGC, CGAAUGU, CCCAUGU, UACAUGC, and UCCAUGU).
Ref: PMID: 38038264.
See for details: Osnaya et al. (2025) cited in the front page of this webpage.