Q: In this task, you are given a sentence. You are expected to recognize the name of gene or protein. Although there might be several correct answers, you need to write one of them.
 We also examined whether signaling by muramyl peptides involves the use of cell surface receptors , including CD14 and Toll - like receptor 2 ( TLR2 ) or TLR4 that are known to be signal - transducing receptors for other bacterial cell wall components .
A:
cell surface receptors