DOMAIN INTERACTIONS AND ANTIGEN-BINDING OF RECOMBINANT ANTI-Z-DNA ANTIBODY VARIABLE DOMAINS - THE ROLE OF HEAVY AND LIGHT-CHAINS MEASURED BY SURFACE-PLASMON RESONANCE
M. Polymenis et Bd. Stollar, DOMAIN INTERACTIONS AND ANTIGEN-BINDING OF RECOMBINANT ANTI-Z-DNA ANTIBODY VARIABLE DOMAINS - THE ROLE OF HEAVY AND LIGHT-CHAINS MEASURED BY SURFACE-PLASMON RESONANCE, The Journal of immunology, 154(5), 1995, pp. 2198-2208
The heavy (H) and light(L) chain V domains of anti-Z-DNA mouse mAb Z22
were expressed separately in bacteria. When mixed in vitro, the V dom
ains associated stoichiometrically to reconstitute the Ag binding site
of Z22, as judged by specific reactivity with Z-DNA and anti-Z22 Id A
bs. The apparent K-d of the Z22 V-H-V-L association was 5.47 x 10(-8)
M, measured by surface plasmon resonance. A replacement at V-L positio
n 96, which reduced Ag binding affinity of a single chain Fv (clone LZ
1-2) by two orders of magnitude, did not reduce the affinity of intera
ction between the V-H and V-L domains (apparent K-d = 1.93 X 10(-8) M
for V-H association with LZ1-2). Fab prepared from native Z22 bound sp
ecifically to a 30-bp Z-DNA oligonucleotide with an apparent K-d = 1.5
6 X 10(-8) M. The V-H domain alone bound Z-DNA specifically with an af
finity similar to that of the Fab or Fv's of Z22 (K-d = 1.68 X 10(-8)
M), whereas Z22 V-L domain alone did not interact with nucleic acids.
Z22 V-H binding to Ag was inhibited by association with the mutant LZ1
-2 V-L. These results indicate that the Z22 H chain makes important co
ntributions to specific binding of Z-DNA. Although the L chain does no
t add greatly to the binding energy, an appropriate L chain is require
d to permit Ag binding in the Fv domain. These in vitro results resemb
le the in vivo modulation of H chain autoreactivity that occurs with L
chain substitution in receptor editing.