Antiproliferative factor (APF) binds specifically to sites within the cytoskeleton-associated protein 4 (CKAP4) extracellular domain.

Background: Antiproliferative factor (APF) is a sialoglycopeptide elevated in the urine of patients with interstitial cystitis-a chronic, painful bladder disease. APF inhibits the proliferation of normal bladder epithelial cells and cancer cells in vitro, presumably by binding to its cellular receptor, cytoskeleton associated-protein 4 (CKAP4); however, the biophysical interaction of APF with CKAP4 has not been characterized previously. In this study, we used surface plasmon resonance (SPR) to explore the binding kinetics of the interaction of APF and as-APF (a desialylated APF analogue with full activity) to CKAP4.

Role of vacuolar membrane proton pumps in the acidification of protein storage vacuoles following germination.

During soybean (Glycine max (L.) Merrill) seed development, protease C1, the proteolytic enzyme that initiates breakdown of the storage globulins β-conglycinin and glycinin at acidic pH, is present in the protein storage vacuoles (PSVs), the same subcellular compartments in seed cotyledons where its protein substrates accumulate. Actual proteolysis begins to be evident 24 h after seed imbibition, when the PSVs become acidic, as indicated by acridine orange accumulation visualized by confocal microscopy.