Structure and function of a cyanophage-encoded peptide deformylase

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Bacteriophages utilize auxiliary metabolic genes for efficient replication.
• Cyanophages maintain host photosynthesis during infection by redirecting energy and reducing power.
• Photosystem II D1/D2 protein photodamage necessitates continuous synthesis, requiring N-terminal formyl group removal by peptide deformylase (PDF).

Purpose of the Study:

• To investigate the presence and function of PDF genes in marine phages.
• To characterize a specific PDF homolog from Synechococcus cyanophage S-SSM7.
• To understand the role of phage-encoded PDF in maintaining host photosynthetic activity.

Main Methods:

• Marine metagenome analysis to identify phage-encoded PDF homologs.
• Sequence and phylogenetic analysis of the identified PDF gene.
• Expression and biochemical characterization of phage and host PDF enzymes.
• X-ray crystallography to determine PDF structures.

Main Results:

• A PDF homolog was identified in Synechococcus cyanophage S-SSM7, belonging to the Type 1B subclass.
• The phage PDF is more active than the host PDF and preferentially deformylates D1 protein N-termini.
• Crystal structures revealed active sites identical to Arabidopsis chloroplast PDF, but lacking a C-terminal α-helix.

Conclusions:

• Cyanophages encode PDF enzymes with a specific preference for D1 protein substrates.
• This phage-encoded PDF contributes to maintaining host photosynthetic activity, enhancing phage replication.
• The findings expand the known repertoire of phage auxiliary metabolic genes involved in host manipulation.