sentence: Interestingly , in the fully-activated structure , according to the mentioned study of Bhattacharya and Vaidehi , the pathway involving the TM7 starts in the extracellular part of TM2 , goes down along this helix and jumps to the TM7 at the height of D2.50 / N7.49 , which are suggested to constitute the allosteric binding site for sodium ions ( Figure 2 ) .