STRUCTURAL COMPARISON OF PROSTATE-SPECIFIC ANTIGEN AND HUMAN GLANDULAR KALLIKREIN USING MOLECULAR MODELING

Objectives. Prostate-specific antigen (PSA), the most useful tumor marker for prostate cancer, is one of three members of the human kallikrein family of serine proteases. PSA and human glandular kallikrein (hK2, previously called hCK-1) share extensive homology and are both produced in the prostate under androgen control. Our goals were to use molecular modeling techniques to generate models of the tertiary structure of PSA and hK2 and to compare their molecular features and areas of homology using these models. Methods. Models of PSA and hK2 were generated by extrapolating from available crystallographic coordinates and amino acid sequences of homologous members of the serine protease family using standard comparative methods. Results. Porcine kallikrein (57% homology) and rat tonin (53% homology) were used as templates for PSA. Porcine kallikrein (67% homology) was used as a template for hK2. The models were superimposed to define regions of nonhomology between PSA and hK2. Conclusions. Three-dimensional protein models of PSA and hK2 were generated. These models have potential uses in analyzing antigen-antibody interactions, modeling of inhibitor complexes of both PSA and hK2, and furthering our understanding of the molecular interactions involved in the clinical detection of PSA and hK2.