Distinct roles of the N- and C-terminal regions of MetW in MetX interaction and activation in Pseudomonas aeruginosa

Abstract

In methionine biosynthesis, homoserine O-acylation is catalyzed by MetX together with its regulatory protein, MetW, in some bacteria. MetW interacts with MetX and regulates its enzymatic activity. Although this interaction and regulation are likely indispensable for efficient methionine biosynthesis, the specific regions of MetW crucial for these functions remain unidentified. Here, we characterize this system using MetW and MetX from Pseudomonas aeruginosa (PaMetW and PaMetX, respectively). We found that the N-terminal region of PaMetW and the C-terminal region of PaMetX are critical for their interaction. Additionally, the C-terminal region of PaMetW is essential for enhancing homoserine O-succinylation activity. Structural models predict that the PaMetW N-terminal region is located near the PaMetX C-terminal region and that the two terminal regions form an intermolecular parallel β-sheet. These results suggest that the N- and C-terminal regions of PaMetW play important roles in the interaction with PaMetX and enhancement of its enzymatic activity, respectively.