Mouse class III myosins: kinase activity and phosphorylation sites.

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Class III unconventional myosins possess an N-terminal kinase domain, suggesting roles in signaling and actin-based transport.
• Human class IIIA myosin, implicated in progressive hearing loss, has motor functions modulated by autophosphorylation, but specific sites remain unidentified.

Purpose of the Study:

• To investigate the kinase activity and identify phosphorylation sites in mouse class III myosins (mMyo3A and mMyo3B).
• To compare these findings with human orthologs and understand phosphorylation-dependent regulation.

Main Methods:

• Enzyme activity assays to confirm kinase function.
• Liquid chromatography-mass spectrometry (LC-MS) to identify phosphorylated sites.
• Bioinformatic analysis to assess conservation of phosphorylation motifs.

Main Results:

• Mouse mMyo3A and mMyo3B kinase domains are active and exhibit similar substrate specificities.
• Autophosphorylation occurs within the kinase, myosin motor, and tail domains of both mMyo3A and mMyo3B.
• Identified phosphorylation sites and motifs are highly conserved across vertebrate class III myosins, including human forms.

Conclusions:

• This study identifies key phosphorylation sites in class III myosins, providing crucial insights into their functional regulation.
• The conserved nature of these sites suggests a fundamental role in the biology of class III myosins across species.