Fig. 1.

Enrichment of ubiquitylated proteins in a low-density membrane fraction of human urine. (A) Immunoblotting of ubiquitin in whole urine, 200,000 × g (200k) “low-density membrane” pellet, and 17,000 × g (17k) pellet of human urine from three groups of pooled samples (G1–3). Each lane is loaded with an equal quantity of total protein. Conjugated Ub signal (observed at >25 kDa) is predominant in the 200k pellet (B), whereas free mono- and di-Ub signal is predominant in the 17k pellet (C). Values are S.E. and *, **, and *** indicate p values of less than 0.05, 0.01, and 0.001, respectively, by one-way analysis of variance (ANOVA) followed Tukey's multiple comparison tests. Data are representative of three individual experiments (see Methods).