text: As in the standard code, initiation is most efficient at AUG.  In addition, GUG and UUG starts are documented in archaea and bacteria.  In Escherichia coli, UUG is estimated to serve as initiator for about 3% of the bacteriums proteins.  CUG is known to function as an initiator for one plasmid-encoded protein (RepA) in E. coli. In addition to the NUG initiations, in rare cases bacteria can initiate translation from an AUU codon as e.g. in the case of poly(A) polymerase PcnB and the InfC gene that codes for translation initiation factor IF3.  The internal assignments are the same as in the standard code though UGA codes at low efficiency for tryptophan in Bacillus subtilis and, presumably, in Escherichia coli'.
  The NCBI raw format is as follows, with UUG, CUG, AUU, AUC, AUA, AUG, and GUG marked as possible initiators:
      AAs  = FFLLSSSSYY**CC*WLLLLPPPPHHQQRRRRIIIMTTTTNNKKSSRRVVVVAAAADDEEGGGG
    Starts = ---M------**--*----M------------MMMM---------------M------------
    Base1  = TTTTTTTTTTTTTTTTCCCCCCCCCCCCCCCCAAAAAAAAAAAAAAAAGGGGGGGGGGGGGGGG
    Base2  = TTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGG
    Base3  = TCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAG
  Initiation at AUC and AUA is not addressed in the NCBI description text, but both are indeed known to occur in E. coli.