MAP 0, a 400-kDa microtubule-associated protein unique to teleost fish.
Microtubules from neural tissues of the Atlantic cod, Gadus morhua, and of several species of Antarctic teleosts are composed of tubulin and several microtubule-associated proteins (MAPs), one of which has an apparent molecular weight of approximately 400-430 kDa. Because its apparent molecular weight exceeds those of the MAP 1 proteins, we designate this high molecular weight teleost protein MAP 0. Cod MAP 0 failed to cross-react with antibodies specific for MAPs 1A, 1B and 2 of mammalian brain, for MAP H1 of squid optic lobe, and for chicken erythrocyte syncolin, which suggests that it has a novel structure. Similarly, MAP 0 from the Antarctic fish was not recognized by an antibody specific for bovine MAP 2. Together, these observations suggest that MAP 0 is a novel MAP that may be unique to fish. To determine the tissue specificity and phylogenetic distribution of this protein, we generated a rabbit polyclonal antibody against cod MAP 0. Using this antibody, we found that MAP 0 was present in microtubule proteins isolated from cod brain tissues and spinal cord but was absent in microtubules from heart, liver, and spleen. At the subcellular level, MAP 0 was distributed in cod brain cells in a punctate pattern coincident with microtubules but was absent in skin cells. MAP 0 was also detected in cells of the peripheral nervous system. A survey of microtubule proteins from chordates and invertebrates showed that anti-MAP 0-reactive homologs were present in five teleost species but not in more primitive fish and invertebrates or in higher vertebrates. MAP 0 bound to cod microtubules by ionic interaction at a site recognized competitively by bovine MAP 2. Although its function is unknown, MAP 0 does not share the microtubule-binding properties of the motor proteins kinesin and dynein. We propose that MAP 0 is a unique, teleost-specific MAP.
Modig
C
C
Department of Zoophysiology, Göteborg University, Sweden.
Rutberg
M
M
Detrich
H W
HW
Billger
M
M
Strömberg
E
E
Wallin
M
M
D000663:Amphibians / Q000378:metabolism*; D000818:Animals; D000918:Antibody Specificity; D002478:Cells, Cultured; D002490:Central Nervous System / Q000737:chemistry; D005399:Fishes / Q000378:metabolism*; D007448:Invertebrates / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000302:isolation & purification*; D008970:Molecular Weight; D009928:Organ Specificity; D017933:Peripheral Nervous System / Q000737:chemistry; D010802:Phylogeny; D012104:Reptiles / Q000378:metabolism*; D013045:Species Specificity; D013347:Subcellular Fractions / Q000737:chemistry
D008869:Microtubule-Associated Proteins