Dimerization seems to present in the E. Coli chemotaxis pathway. The aspartate receptor involved in chemotaxis, Tar, is a symmetric homodimer that binds to aspartate. binding of ligand promotes receptor dimerization. There has been fusion of Tar to EnvZ such that aspartate no longer induces chemotaxis but osmolarity responses. Also, the same type of experiment was done with the insulin receptors's signaling domain and it has insulin-like tyrosine kinase activity in response to aspartate. Although, dimerization of Tar may not be the only mechanism. However, dimerization seems to be a pre-requisite to function.