Distribution of proteins cross-reacting with ab-MF3 and ab-MF16 in rat liver subcellular fractions. Protein (100 μg), present in rat liver homogenates, subcellular fractions, and purified peroxisomes, or, in the case of the peroxisomal subfractions, the amount of protein extracted from 100 μg of total peroxisomal proteins, was subjected to SDS/PAGE, transferred to nitrocellulose, and immunoblotted with ab-MF3 (A) or ab-MF16 (B). H, homogenate; E, postnuclear supernatant; N, nuclear fraction; M, heavy mitochondrial fraction; L, light mitochondrial fraction; P, microsomal fraction; S, cytosol; PO, purified total peroxisomes; and PO′, purified total peroxisomes of a clofibrate-treated rat. S1, P1, S2, and P2 are peroxisomal subfractions corresponding to the (S) supernatant and (P) pellet of (1) 10 mM pyrophosphate (pH 9.0) and (2) 100 mM sodium carbonate (pH 11.0) extractions, respectively. The migration of the molecular mass markers (expressed in kDa) is indicated. An arrow is used to demark PMP57 (see text). Migration of the peroxisomal proteins urate oxidase (UOX), catalase (CAT), and the inducible multifunctional protein (MFP) are also indicated (see Materials and Methods).