TY - JOUR
T1 - Antiferritin VL homodimer binds human spleen ferritin with high specificity
AU - Nymalm, Yvonne
AU - Kravchuk, Zinaida
AU - Salminen, Tiina
AU - Chumanevich, Alexander A.
AU - Dubnovitsky, Anatoly P.
AU - Kankare, Jussi
AU - Pentikäinen, Olli
AU - Lehtonen, Jukka
AU - Arosio, Paolo
AU - Martsev, Sergey
AU - Johnson, Mark S.
PY - 2002/6
Y1 - 2002/6
N2 - The antiferritin variable light domain (VL) dimer binds human spleen ferritin ( approximately 85% L subunits) but with approximately 50-fold lower affinity, K(a)=4 x 10(7) x M(-1), than the parent F11 antibody (K(a)=2.1 x 10(9) x M(-1)). The VL dimer does not recognize either rL (100% L subunits) or rH (100% H subunits) human ferritin, whereas the parent antibody recognizes rL-ferritin. To help explain the differences in ferritin binding affinities and specificities, the crystal structure of the VL domain (2.8A resolution) was determined by molecular replacement and models of the antiferritin VL-VH dimer were made on the basis of antilysozyme antibody D1.3. The domain interface is smaller in the VL dimer but a larger number of interdomain hydrogen bonds may prevent rearrangement on antigen binding. The antigen binding surface of the VL dimer is flatter, lacking a negatively charged pocket found in the VL-VH models, contributed by the CDR3 loop of the VH domain. Loop CDR2 (VL dimer) is located away from the antigen binding site, while the corresponding loop of the VH domain would be located within the antigen binding site. Together these differences lead to 50-fold lower binding affinity in the VL dimer and to more restricted specificity than is seen for the parent antibody.
AB - The antiferritin variable light domain (VL) dimer binds human spleen ferritin ( approximately 85% L subunits) but with approximately 50-fold lower affinity, K(a)=4 x 10(7) x M(-1), than the parent F11 antibody (K(a)=2.1 x 10(9) x M(-1)). The VL dimer does not recognize either rL (100% L subunits) or rH (100% H subunits) human ferritin, whereas the parent antibody recognizes rL-ferritin. To help explain the differences in ferritin binding affinities and specificities, the crystal structure of the VL domain (2.8A resolution) was determined by molecular replacement and models of the antiferritin VL-VH dimer were made on the basis of antilysozyme antibody D1.3. The domain interface is smaller in the VL dimer but a larger number of interdomain hydrogen bonds may prevent rearrangement on antigen binding. The antigen binding surface of the VL dimer is flatter, lacking a negatively charged pocket found in the VL-VH models, contributed by the CDR3 loop of the VH domain. Loop CDR2 (VL dimer) is located away from the antigen binding site, while the corresponding loop of the VH domain would be located within the antigen binding site. Together these differences lead to 50-fold lower binding affinity in the VL dimer and to more restricted specificity than is seen for the parent antibody.
KW - Amino Acid Sequence
KW - Antibodies/chemistry
KW - Binding Sites
KW - Crystallography, X-Ray
KW - Dimerization
KW - Dose-Response Relationship, Drug
KW - Ferritins/chemistry
KW - Humans
KW - Hydrogen Bonding
KW - Kinetics
KW - Models, Molecular
KW - Molecular Sequence Data
KW - Protein Binding
KW - Protein Structure, Secondary
KW - Protein Structure, Tertiary
KW - Sequence Homology, Amino Acid
KW - Spleen/metabolism
U2 - 10.1016/s1047-8477(02)00015-1
DO - 10.1016/s1047-8477(02)00015-1
M3 - Article
C2 - 12217656
SN - 1047-8477
VL - 138
SP - 171
EP - 186
JO - Journal of Structural Biology
JF - Journal of Structural Biology
IS - 3
ER -