Chemotactic transducer for aerotaxis. Expression is regulated by the transcriptional regulatory protein of anaerobic gene expression, ANR. Both ANR box1 and box2 are required for the functioning of the aer promoter. Mutant shows decreased aerotaxis. Aerotaxis is abolished in the aer-mcpB double mutant. Belongs to the methyl-accepting chemotaxis (MCP) protein family.