Identification of an alternative translation initiation site for the Pantoea ananatis lycopene cyclase (crtY) gene in E. coli and its evolutionary conservation.
Previous sequence analyses of the lycopene cyclase gene (crt Y) from Pantoea ananatis revealed that translation of its protein product in Escherichia coli began at the ATG start codon. We found, however, that this enzyme could also be produced in E. coli without the ATG start codon present. Results of experiments using crt Y mutants revealed that a GTG (Val) sequence, located in-frame and 24 bp downstream of the ATG, could act as a potential start codon. Additionally, a point-mutated GTA (Val), replaced from alternative GTG start codon, also displayed its potential as a start codon although the strength as a translation initiation codon was considerably weak. This finding suggests that non-ATG codons, especially one base pairing with the anticodon (3'-UAC-5') in fMet-tRNA, might be also able to function as start codon in translation process. Furthermore, amino acid sequence alignment of lycopene cyclases from different sources suggested that a Val residue located within the N-terminus of these enzymes might be used as an alternative translation initiation site. In particular, presence of a conserved Asp, located in-frame and 12 bp upstream of potential start codon, supports this assumption in view of the fact that Asp (GAT or GAC) can function as part of the Shine-Dalgano sequence (AGGAGG).
Kim
Sung-Woo
SW
AceBiotech Co., Ltd., #114 Bio-Venture Center, KRIBB, Yuseong, Daejeon 305-806, Republic of Korea.
Jung
Woo-Hyuk
WH
Ryu
Ji-Myung
JM
Kim
Jae-Bum
JB
Jang
Hyung-Wook
HW
Jo
Young-Bae
YB
Jung
Joon-Ki
JK
Kim
Jung-Hoe
JH
D000595:Amino Acid Sequence; D001483:Base Sequence; D002338:Carotenoids / Q000378:metabolism; D018387:Codon, Initiator; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D015964:Gene Expression Regulation, Bacterial; D019753:Intramolecular Lyases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D020636:Pantoea / Q000201:enzymology* / Q000235:genetics; D016415:Sequence Alignment; D014158:Transcription, Genetic
D018387:Codon, Initiator; D002338:Carotenoids; D019753:Intramolecular Lyases; C070925:lycopene cyclase-isomerase