J. Biol. Chem., Vol. 264, Issue 30, 17691-17697, 10, 1989
Biotinylation of reactive amino groups in native recombinant human interleukin-1 beta
AW Yem, HA Zurcher-Neely, KA Richard, ND Staite, RL Heinrikson and MR Deibel Jr
Department of Biopolymer Chemistry, Upjohn Company, Kalamazoo, Michigan 49001.
Recombinant human interleukin-1 beta (rIL-1 beta) was chemically modified
by a 10-fold molar excess (reagent:protein) of sulfosuccinimidyl
6-(biotinamido) hexanoate (sulfo-NHS-LC-biotin) or sulfosuccinimidobiotin
(sulfo-NHS-biotin) under mild conditions. The primary product was purified
in each case by cation exchange high performance liquid chromatography
(HPLC) and digested with endoproteinase Lys C. Peptide mapping by C18
reverse phase HPLC permitted identification of three sites of biotinylation
using both reagents; N-terminal alanine, lysine 93, and lysine 94. Few
additional singly modified rIL-1 beta products were obtained under these
conditions, despite the presence of 15 lysine residues in this protein.
These data support the view that the N terminus as well as the trilysine
sequence (residues 92-94) are readily susceptible to chemical modification
and are exposed on the surface of the protein. Chromatography of intact
biotinylated rIL-1 beta by C4 reverse phase HPLC resolved a protein
modified exclusively at the N-terminal alanine from two proteins modified
singly at either lysine 93 or lysine 94. In addition, a protein product
modified at lysine 103 was also obtained when rIL-1 beta was similarly
modified with sulfo-NHS-biotin. Since the only difference between the two
biotinylation reagents relates to spacer length and its associated
hydrophobicity, these data suggest that lysine 103 is not as accessible to
surface modification reagents as are lysine 93, lysine 94, or alanine 1.
Initial experiments indicate that none of the modifications described above
decrease thymocyte proliferation by more than one order of magnitude.
Therefore, these amino acid residues are not crucial for bioactivity, and
we anticipate the use of these monobiotinylated proteins in
structure/function analysis of IL-1 beta.