(b) HeLa cells were co-transfected with ULK1-Myc alone or in combination with wild-type ubiquitin or its mutant (K48R or K63R) HA-tagged constructs. Protein extracts were immunoprecipitated using an anti-Myc antibody. Purified complexes and total extracts were analysed by western blotting using anti-Myc and anti-HA antibodies. 