Final answer:
CheB is the Che protein responsible for removing methyl groups from MCP proteins, a critical step in bacterial chemotaxis. This methyl esterase ensures the bacteria can adapt to changes in environmental chemical gradients by adjusting its motility.
Step-by-step explanation:
The Che protein that removes methyl groups from MCP (methyl-accepting chemotaxis protein) proteins is CheB. The process by which CheB demethylates the MCP proteins is essential for the proper functioning of bacterial chemotaxis. When MCP proteins are methylated by CheR, they are active in signaling; however, the methylation state is fine-tuned by CheB, which acts as a methylesterase to remove methyl groups. This mechanism allows bacteria to adapt to varying concentrations of chemical attractants and repellents in their environment by altering their swimming behavior accordingly.
In broader biochemical contexts, protein modification and removal is a common post-translational modification. While N-formyl methionine (in prokaryotes) or methionine (in eukaryotes) and some other amino acids are typically removed from the N-terminal or C-terminal ends enzymatically, CheB specifically targets the lysine residues in MCP proteins for demethylation. In eukaryotic cells, many proteins undergo modification where the amino group of the amino terminal residue is acetylated, influencing protein stability and interaction.