Pilin Processing Follows a Different Temporal Route than That of Archaellins in Methanococcus maripaludis

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Methanococcus maripaludis possesses two surface appendages: type IV-like pili and archaella.
• Both structures are assembled via a bacterial type IV pilus mechanism and composed of pilin or archaellin subunits.
• Both subunit types are initially preproteins requiring signal peptide removal by specific peptidases (FlaK for archaellins, EppA for pilins) and undergo N-linked glycosylation.

Purpose of the Study:

• To investigate the order of post-translational modifications (signal peptide removal and N-glycosylation) for archaellins and pilins in M. maripaludis.
• To determine if N-glycosylation is a prerequisite for signal peptide removal or vice versa for these appendages.

Main Methods:

• Investigated FlaK processing of archaellins with and without N-glycosylation.
• Examined EppA processing of pilins with and without N-glycosylation.
• Analyzed the impact of signal peptide presence/absence on glycosylation status.

Main Results:

• Archaellins can be processed by FlaK independently of N-glycosylation.
• N-glycosylation can occur on archaellins while their signal peptides are still attached.
• Pilins require signal peptide removal by EppA before N-glycosylation can occur, although EppA can process non-glycosylated pilins.

Conclusions:

• There is a significant difference in the order of post-translational modifications between archaellins and pilins in M. maripaludis.
• These findings highlight distinct processing pathways for structurally similar type IV pilin-like proteins.