Proteolytic Post-Translational Processing of Adhesins in a Pathogenic Bacterium

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Mollicutes, like mycoplasmas and spiroplasmas, are considered "minimal cells" with small genomes.
• Recent findings reveal complex post-translational modifications in Mollicutes, challenging the minimal cell concept.
• Pathogenic Mollicutes exhibit sophisticated mechanisms, including protein processing, for host interaction.

Purpose of the Study:

• To investigate post-translational modifications of Spiroplasma citri GII-3 adhesion-related protein (ScARP) adhesins.
• To elucidate the mechanism and regulation of ScARP targeted cleavage.
• To explore the functional significance of ScARP processing in host-pathogen interactions.

Main Methods:

• In vitro cleavage assays of ScARP adhesins.
• Analysis of factors influencing cleavage efficiency (pH, antibodies).
• Identification of cleavage sites and characterization of the protease involved.

Main Results:

• ScARP adhesins are processed via ATP-dependent targeted cleavage.
• Cleavage is enhanced by decreased extracellular pH or anti-ScARP antibodies, suggesting surface charge/conformation influence.
• Cleavage sites are in disordered regions, mediated by a non-conventional protease with specific metal ion requirements.

Conclusions:

• Post-translational cleavage of adhesins is a common feature in Mollicutes, enabling adaptation with minimal genomes.
• ScARP processing may facilitate Spiroplasma citri colonization of insect host cells.
• This proteolytic mechanism highlights hidden complexity in "minimal" bacteria.