The additional methionine residue at the N-terminus of bacterially expressed human interleukin-2 affects the interaction between the N- and C-termini.
To gain insight into the origin of the difference in isoelectric point (pI) values for wild-type human interleukin-2 (IL-2) and IL-2 with an additional methionine residue at the N-terminus (Met-IL-2), conformational properties of the two molecular forms of IL-2 were compared by utilizing 1H NMR spectroscopy. Although overall conformations were conserved in the two forms, the presence of the additional methionine residue at the N-terminus induced chemical shift changes for residues Ala1 to Lys8 as well as for Thr133, which is located at the C-terminus. These observations indicate that the effect of the additional methionine residue is confined to the N- and C-terminal regions and unveil the existence of an interaction between the N- and C-terminal regions. The chemical shift change observed for Thr133 can be interpreted in terms of a change in pKa of the C-terminal carboxyl group, which interacts differently with the N-terminal amino group in the two forms of IL-2. It seems to be reasonable to conclude that the difference in pI values for the two forms of IL-2 is the consequence of the different interactions between the C- and N-terminal residues.
Endo
S
S
Pharmaceutical Research Division, Takeda Chemical Industries, Ltd., Yodogawa-ku, Osaka 532-8686, Japan. Endo_Satoshi@takeda.co.jp
Yamamoto
Y
Y
Sugawara
T
T
Nishimura
O
O
Fujino
M
M
D004926:Escherichia coli / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D007376:Interleukin-2 / Q000031:analogs & derivatives / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008715:Methionine / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism
D007376:Interleukin-2; D010446:Peptide Fragments; D011994:Recombinant Proteins; D008715:Methionine