The genome of Plasmodium falciparum contains a small gene family that expresses proteins characterized by the presence of 6-cysteine domains. Most of these proteins are expressed on the surface of the parasite and some are known to play a role in cell-cell interactions. Two members of this family, Pfs48/45 and Pfs230, form a complex localized on the surface of gametes and are recognized as important targets for transmission-blocking vaccines. In this study we report the analysis of an additional member of this family, Pfs47 the closest paralog of Pfs48/45. We demonstrate that Pfs47 is expressed only in female gametocytes and is located on the surface of female gametes following emergence from red blood cells. In contrast to the critical function of P48/45 for male fertility, Pfs47 does not appear crucial for female fertility. Parasites lacking Pfs47 through targeted gene disruption, produce normal numbers of oocysts when included in the blood meal of the mosquito vector. In addition, three monoclonal antibodies against Pfs47 were unable to inhibit oocyst development when present in a blood meal containing wild type parasites. These results show redundancy in protein function for Pfs47 and reduce the support for candidacy of Pfs47 as a transmission-blocking vaccine target. (c) 2006 Elsevier B.V. All rights reserved.