[1] G418 blocks polypeptide synthesis by inhibiting the elongation step in both prokaryotic and eukaryotic cells.

[1] Resistance to G418 is conferred by the neo gene from Tn5 encoding an aminoglycoside 3'-phosphotransferase, APT 3' II.

Researchers can link the neoR selective resistance gene with their vector.

[1][5] G418 Disulfate and other aminoglycosides prevent protein synthesis at the early stages of elongation, post-initiation, initiation of translation.

Cells transfected with resistance plasmids containing the neo gene can express aminoglycoside 3'-phosphotransferase (APT 3' I or APT 3' II) which covalently modifies G418 to 3-phosphoric G418,  which has negligible potency and has low-affinity for prokaryotic and eukaryotic ribosomes.