INVESTIGADORES
FERREIRO Diego Ulises
artículos
Título:
Specific antibody-DNA interaction: a novel strategy for tight DNA recognition
Autor/es:
DI PIETRO SM, CENTENO JM, CERUTTI ML, LODEIRO MF, FERREIRO DU, ALONSO LG, SCHWARZ FP, GOLDBAUM FA, DE PRAT-GAY G.
Revista:
BIOCHEMISTRY
Referencias:
Año: 2003 vol. 42 p. 6218 - 6227
ISSN:
0006-2960
Resumen:
Anti-double-stranded DNA monoclonal antibodies
against a viral transcriptional regulatory site are capable of
discriminating single-base replacements with affinities of 1 x 10(-)(9)
M, which were optimized for the length of the duplex used as the
immunogen. Their affinity for DNA duplexes of increasing length is
lower, but reaches a plateau at 2 x 10(-)(8) M, still a fairly high
affinity compared to those of most known natural anti-DNA antibodies.
The ability of the antibodies to bind to a 166 bp DNA fragment
containing the specific sequence strongly suggests that these have the
potential of binding the specific sequence within larger genomic DNA
fragments. Electrostatic interactions do not play a significant role,
the opposite of what is observed in natural DNA binding interfaces. In
addition, the insensitivity of the antibody-DNA interaction to solute
effects is indicative of a marginal participation of water molecules at
the interface compared to the level of participation at the natural
E2-DNA interface. Spectroscopic evidence of base unstacking strongly
suggests substantial denaturation of antibody-bound DNA, in agreement
with thermodynamic results that show an unusual positive heat capacity
change, which could be explained at least in part by the exposure of
DNA bases upon binding. Lower local DNA stability cooperates with
sequence recognition in producing the highest binding affinity. A slow
rate of antibody-DNA association indicates an energy barrier imposed by
conformational rearrangements, as opposed to an electrostatically
assisted diffusion-controlled collision in the E2 DNA binding domain.
While the E2-DNA interaction takes place through a typical direct
readout mechanism, the anti-double-stranded DNA monoclonal antibody-DNA
interaction could be viewed as a distinctive case of indirect readout
with a significant distortion in the DNA conformation. However, the
precise mechanism with which the DNA bases are accommodated in the
antibody combining site will require structural analysis at atomic
resolution. These results constitute a first stage for unveiling the
unusual molecular recognition mechanism of a specific DNA sequence by
antibodies. This mechanism could represent the strategy with which the
immune system tightly and specifically recognizes a DNA antigen.