The 72-kDa microtubule-associated protein from porcine brain.
A microtubule-associated protein (MAP) with a molecular mass of 72-kDa that was purified from porcine brain by using its property of heat stability in a low pH buffer was characterized. Low-angle rotary shadowing revealed that the 72-kDa protein was a rodlike protein approximately 55-75 nm long. The 72-kDa protein bound to microtubules polymerized from phosphocellulose column-purified tubulin (PC-tubulin) with taxol and promoted the polymerization of PC-tubulin in the absence of taxol. Microtubules polymerized by the 72-kDa protein showed a tendency to form bundles of several microtubules. Quick-freeze, deep-etch electron microscopy revealed that the 72-kDa protein formed short crossbridges between microtubules. We performed peptide mapping to analyze the relationship of the 72-kDa protein to other heat-stable MAPs, and the results showed some resemblance of the 72-kDa protein to MAP2. Cross-reactivity with a monoclonal anti-MAP2 antibody further suggested that the 72-kDa protein and MAP2 are immunologically related. To study the relationship between the 72-kDa protein and MAP2C, a smaller molecular form of MAP2 identified in juvenile rat brain, we prepared the 72-kDa protein from rat brain by the same method as that used for porcine brain. The fact that the 72-kDa protein from juvenile rat brain was also stained with our monoclonal anti-MAP2 antibody also suggested that the 72-kDa protein is an MAP2C homologue of the porcine brain.
Takeuchi
M
M
Department of Anatomy and Cell Biology, Faculty of Medicine, University of Tokyo, Japan.
Hisanaga
S
S
Umeyama
T
T
Hirokawa
N
N
D000818:Animals; D000906:Antibodies; D001921:Brain / Q000378:metabolism*; D015151:Immunoblotting; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000276:immunology / Q000302:isolation & purification*; D008870:Microtubules / Q000378:metabolism / Q000648:ultrastructure; D008968:Molecular Conformation; D008970:Molecular Weight; D010449:Peptide Mapping; D011108:Polymers / Q000378:metabolism; D051381:Rats; D013552:Swine
D000906:Antibodies; D008869:Microtubule-Associated Proteins; D011108:Polymers