The ATP-binding and ATPase activities of human papillomavirus type 16 E1 are significantly weakened by the absence of prolines in its ATP- binding domain -- Raj and Stanley 76 (12): 2949 -- Journal of General Virology

The E1 protein of human papillomavirus (HPV) type 16 is the only known papillomavirus E1 which does not contain any proline residues in the phosphate-loop (P-loop) of its ATP-binding site. To ascertain whether this feature influences the activities of HPV-16 E1, we generated a mutant HPV-16 E1 (E1Pro) in which prolines are inserted in place of alanines in this site, making the P-loop identical to its bovine papillomavirus type 1 counterpart. Glutathione S-transferase (GST) fusion proteins (GSTE1wt and GSTE1Pro) were produced, purified and used to assay for ATP-binding ability, ATPase activity and ability to complex with the HPV-16 E2 protein. The results show that the lack of prolines in the P-loop, which is unique to HPV-16 E1, significantly weakens its ATP-binding and ATPase activities without affecting its ability to complex with the HPV-16 E2 protein.