Molecular characterization reveals identity of microtubule-associated proteins MAP3 and MAP4

The identity of two microtubule-associated proteins, MAP3 and MAP4, was ver ified both immunologically and biochemically. MAP3 was enriched from the he at-stable fraction of rat brain extracts by reverse-phase HPLC and preparat ive two-dimensional gel electrophoresis, Both MAP3 and MAP4 antibodies reac ted with the corresponding spots on two-dimensional Western blots. Amino ac id sequences of internal peptides derived from rat MAP3 matched with corres ponding sequence stretches of mouse MAP4. In the kidney cortex, the MAP3 an tibody stained not only glomerular podocytes but also interstitial cells. T his distribution pattern of MAP3 is identical to that of MAP4 reported prev iously. These results indicate that MAP3 and MAP4 are identical. (C) 2000 A cademic Press.