Loading…
A kinase-related protein stabilizes unphosphorylated smooth muscle myosin minifilaments in the presence of ATP
An apparent paradox in smooth muscle biology is the ability of unphosphorylated myosin to maintain a filamentous structure in the presence of ATP in vivo, whereas unphosphorylated myosin filaments are depolymerized in vitro in the presence of ATP. This suggests that additional uncharacterized factor...
Saved in:
Published in: | The Journal of biological chemistry 1993-08, Vol.268 (22), p.16578-16583 |
---|---|
Main Authors: | , , , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that cite this one |
Online Access: | Get full text |
Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
Summary: | An apparent paradox in smooth muscle biology is the ability of unphosphorylated myosin to maintain a filamentous structure
in the presence of ATP in vivo, whereas unphosphorylated myosin filaments are depolymerized in vitro in the presence of ATP.
This suggests that additional uncharacterized factors are required for the stabilization of myosin filaments in the presence
of ATP. We report here that an abundant smooth muscle protein forms sedimentable complexes with unphosphorylated smooth muscle
myosin, partially reverses the depolymerizing effect of ATP on unphosphorylated myosin, and promotes the assembly of minifilaments
as revealed by electron microscopy. This protein is called kinase-related protein (KRP) because it is derived from a gene
within the gene for myosin light chain kinase (MLCK) and has an amino acid sequence identical to the carboxyl-terminal domain
of MLCK. Consistent with the results with purified KRP, deletion of the KRP domain within MLCK results in a diminished ability
of MLCK to interact with unphosphorylated myosin. KRP binds to the heavy meromyosin fragment of myosin but not to myosin rod
or fragments lacking the hinge region and light chains. Altogether, these results suggest that KRP may play a critical role
in stabilizing unphosphorylated myosin filaments and that the KRP domain of MLCK may be important for subcellular targeting
to filaments. |
---|---|
ISSN: | 0021-9258 1083-351X |
DOI: | 10.1016/s0021-9258(19)85458-3 |