Figure 3.

Differential extraction of egg membranes of Xenopus expressing either lamin Flag-B3a or Flag-B3b. Oocytes were injected with RNA encoding either lamin Flag-B3a or Flag-B3b. Oocytes were matured to eggs with progesterone, and egg homogenates were prepared by low-speed centrifugation. Extracts were diluted in buffer (see MATERIALS AND METHODS) and separated into a supernatant (S1) and a pellet. The pellet was resuspended in buffer containing 4 M urea and separated again into a supernatant (S2) and a pellet. This pellet was resuspended in buffer containing 1% NP-40 and separated into a supernatant (S3) and a pellet (P3). The fractions were separated by SDS-PAGE, and epitope-tagged lamins were detected by immunoblotting with mAb M2. The sizes of molecular mass markers are given in kilodaltons at the right.