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Intracellular targeting of isoproteins in muscle cytoarchitecture

B W Schäfer1, J C Perriard

  • 1Institute for Cell Biology, Swiss Federal Institute of Technology, Zurich.

The Journal of Cell Biology
|April 1, 1988
PubMed

Insights

Muscle creatine kinase (MM-CK) specifically binds to the M-band in chicken myofibrils. This binding requires the tail portion of MM-CK, not its head, highlighting targeted molecular function.

Area of Science:

  • Molecular Biology
  • Cellular Biology
  • Biochemistry

Background:

  • Muscle creatine kinase (MM-CK) is found in the M-band of chicken skeletal muscle myofibrils.
  • Chicken heart cells express BB-CK but not MM-CK and do not show this M-band association.
  • This suggests a specific interaction mechanism for MM-CK localization.

Purpose of the Study:

  • To investigate the specificity of MM-CK interaction with the myofibril M-band.
  • To determine which part of the MM-CK molecule is responsible for M-band targeting.

Main Methods:

  • Cultured chicken heart cells were used as a model system ('living test tubes').
  • Microinjection of in vitro synthesized MM-CK and hybrid M-CK/B-CK mRNA.
  • Detection of translation products using isoprotein-specific antibodies.

Main Results:

  • Injected MM-CK molecules localized to the M-band of myofibrils.
  • Chimeric proteins with the tail half of M-CK and head half of B-CK also localized to the M-band.
  • The tail portion of M-CK, but not the head, was essential for M-band association.

Conclusions:

  • The tail domain of MM-CK is critical for its specific targeting to the myofibril M-band.
  • Molecular targeting, rather than just biochemical properties, dictates MM-CK's role in cell cytoarchitecture.
  • Specific functional roles can depend on precise localization within cellular compartments.

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