Investigation of active form of catalytic antibody light chain 41S-2-L

Abstract: We have raised a monoclonal antibody (41S-2) against the conserved sequence, RGPDRPEGIEEEGGERDRD, of human immunodeficiency virus type1 (HIV-1) envelope gp41. That antibody light chain (41S-2-L) cleaves gp41-derived peptide (TPRGPDRPEGIEEEGGERDRD; TP41-1) with a characteristic biphasic profile composed of induction and active phases. It is considered that the conformation of 41S-2-L is changed, by such as induced fitting, to move to active phase to decompose the antigenic peptide during the induction phase. In order to investigate what happens to 41S-2-L in the induction and active phase, the cleavage reaction of the peptide by 41S-2-L was examined in detail from the viewpoint of kinetic and spectroscopic analysis. The kinetic data showed that the preferable conformational transition of 41S-2-L took place by the unimolecular reaction of 41S-2-L in the induction phase. UV–vis and fluorescence spectroscopic analysis suggested that the conformational transition leads to the generation of aggregates of 41S-2-L in the reacting solution, which causes the huge enhancement of the catalytic activity of 41S-2-L. The nuclei of the aggregates may be formed in the induction phase. The aggregates and soluble 41S-2-L are considered to be in chemical equilibrium during the cleavage reaction of the antigen. [Copyright &y& Elsevier]