The mechanism of equilibrium binding of microtubule-associated protein 2 to microtubules. Binding is a multi-phasic process and exhibits positive cooperativity

The mechanism of binding of microtubule-associated protein 2 (MAP2) to taxol-stabilized microtubules (MTs) was examined through Scatchard analysis of equilibrium binding and by immunoelectron microscopy. We demonstrate the following. 1) Binding is a cooperative process as indicated by sigmoidal bind...

Full description

Saved in:
Bibliographic Details
Published in:The Journal of biological chemistry 1993-07, Vol.268 (20), p.15158-15167
Main Authors: WALLIS, K. T, SALMAN AZHAR, RHO, M. B, LEWIS, S. A, COWAN, N. J, MURPHY, D. B
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Brain - metabolism
Cattle
Cell structures and functions
Chickens
Cytoskeleton, cytoplasm. Intracellular movements
Fundamental and applied biological sciences. Psychology
Mice
Microscopy, Immunoelectron
Microtubule-Associated Proteins - metabolism
Microtubules - drug effects
Microtubules - metabolism
Microtubules - ultrastructure
Molecular and cellular biology
Neurons - metabolism
Paclitaxel - pharmacology
Protein Binding
Solvents
Tubulin - metabolism
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The mechanism of binding of microtubule-associated protein 2 (MAP2) to taxol-stabilized microtubules (MTs) was examined through Scatchard analysis of equilibrium binding and by immunoelectron microscopy. We demonstrate the following. 1) Binding is a cooperative process as indicated by sigmoidal binding curves, prominent humps in Scatchard plots, and an all-or-none response in binding during ligand titrations. At high tubulin/MAP2 ratios, the Kd for noncontiguous binding (5-25 microM) is estimated to be 100-1500 times greater than that predicted for contiguous binding, suggesting a high degree of cooperativity. 2) Cooperativity is indicated independently by a highly clustered or patchy distribution of MAP2 on MTs as revealed by immunoelectron microscopy. 3) The binding of truncated constructs of mouse MAP2 protein suggests that a domain of MAP2 conferring cooperativity is located in or near the MT binding site near the carboxyl terminus. We speculate that in the cell, cooperativity may generate MTs with uniform biochemical properties and contribute to the segregation of MAPs in neuronal cell processes.
ISSN:0021-9258
1083-351X
DOI:10.1016/s0021-9258(18)82450-4