RELATIVE CONFORMATIONAL STABILITIES OF SINGLE-CHAIN POCKET AND GROOVE-SHAPED ANTIBODY ACTIVE-SITES INCLUDING HCDR TRANSPLANT INTERMEDIATES

Stability measurements of SCA 04-01/212 (anti-ssDNA) which possesses a groove-shaped active site were performed by Gdn-HCl-induced unfolding , analyzed assuming a simple two-state equilibrium, and expressed as t he free energy of unfolding, Delta G(n-u) A Delta G(n-u) of 1.44 +/- 0 .13 kcal/mol was determined experimentally for SCA 04-01/212. In addit ion, the conformational stabilities of HCDR transplants, hybrid antibo dy molecules resulting from the transplantation of HCDRs from SCA 4-4- 20 (anti-fluorescein) into the corresponding regions of 04-01 in all c ombinations, were determined using the identical protocol applied to S CA 04-01. On the basis of the results of these stability experiments, the HCDR transplants were categorized into three groups, representing low, intermediate, and high stability. Data were discussed in terms of the relationships between structure-function and conformational stabi lity pertaining to the groove-shaped antibody active site of SCA 04-01 /212 and the pocket-shaped active site of SCA 4-4-20/212.