Schematic representation of CXCR4 receptor and mutants.

The 7 transmembrane domain structure is depicted. The truncated CXCR4.7TM mutant was generated by introducing a stop codon after the residue 308. The intracellular loops of CXCR4 subjected to mutagenesis are represented in bold. CXCR4.ICL1m, CXCR4.ICL2m, CXCR4.ICL2mDRY, and CXCR4.ICL3m were constructed by substituting the native loop sequences at the positions indicated with a modified ICL1 loop unable to transduce a signal.