Preferred MRT polypeptides include, for example, at least one transmembrane binding domain which has at least about 40%, more preferably at least about 50%, 55%, 60%, 70%, 80% or 90% amino acid sequence identity with an amino acid sequence shown in SEQ ID NO:2, {HEAD ~ SEQ ID NO:4}, SEQ ID NO:6, {TAIL ~ SEQ ID NO:8} or SEQ ID NO:14, and at least one histidine rich domain 
Preferred MRT polypeptides include , for example , at least one transmembrane binding domain which has at least about 40 % , more preferably at least about 50 % , 55 % , 60 % , 70 % , 80 % or 90 % amino acid sequence identity with an amino acid sequence shown in SEQ ID NO:2 , { HEAD ~ SEQ ID NO:4 } , SEQ ID NO:6 , { TAIL ~ SEQ ID NO:8 } or SEQ ID NO:14 , and at least one histidine rich domain
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