Abstract

The gene products of capB, p34 and p31, were previously isolated by co-purification with the cAMP binding protein CABP1 encoded by the capB homolog capA. The GAL4 two-hybrid system was used to screen a Dictyostelium discoideum cDNA expression library to identify proteins that interacted with p34/31. The clones were tested to eliminate false positives. DNA sequencing analysis revealed that the cDNAs isolated encoded: p34/31; CABP1B, the smaller product of capA; TopA, a mitochondrial type II topoisomerase; and a previously unidentified polypeptide (clone 101) with homology to a bacterial ORF. It was also determined that the product of clone 101 interacted with the gene products of capA in the two-hybrid system. The interactions between p34/31 and TopA, coupled with the results of previous mutation and localization studies, suggest a role for these polypeptides in mitochondrial function. Moreover the isolation of cDNAs encoding CABP1B and the detection of interactions between polypeptide 101 and the capA gene products may imply that p34/31 have more than one intracellular role.