50 μg of testis extract in RIPA buffer was separated by 8% SDS-PAGE and electrotransferred onto a Pure Nitrocellulose membrane (Bio-Rad, http://www.biorad.com). The membrane was incubated with a polyclonal rabbit anti-human TRIP13 antibody (18-003-42687; Genway, http://www.genwaybio.com). According to the manufacturer, the immunogen was a synthetic peptide embedded in sequence we deduced to correspond to exon 3. Binding was detected by chemiluminescence ECL kit (Pierce) using a rabbit anti-chicken IgG horseradish peroxidase conjugate (Pierce).