Mitochondrial lysates from (A) resting or (B) anti-CD3/CD28-stimulated WT or SLP-2 T-KO T cells were layered onto 10–30% discontinuous sucrose gradients. Following sedimentation, 14 equal fractions were collected with fraction 1 starting from the top (10% sucrose) to fraction 14 at the bottom (30% sucrose) of the column. The total protein content of each fraction was resolved by SDS-PAGE then transferred to membranes that were blotted against anti-MRPS15, anti-MRPS22, anti-MRPL44, anti-MRPL14, anti-SLP-2, and anti-PHB2 antibodies. Fractions corresponding to the small (i.e., 28S) and large (i.e., 39S) mitoribosomal subunits, as well as the assembled mitoribosome (i.e., 55S) are indicated. Fraction numbers are indicated for each set of blots. Data are representative of two (A) or three (B) independent experiments.