This phenomenon is proving particularly true of the male gametes, which must complete several complex phases maturation in order to gain the functional competence to engage in one of the most intricate of all cellular interactions, fertilization. Among this multitude of functions, the ability of chaperones to mediate the assembly of oligomeric complexes is of particular interest as advances in functional proteomics have revealed that a significant portion of a cell's proteome realize their functional potential in multiprotein complexes rather than as singular entities ( Sali et al. The heat shock proteins (HSPs), among other ubiquitous chaperone families, have well-documented roles in preventing the aberrant association or aggregation of proteins in addition to facilitating protein synthesis, translocation, de novo folding, and higher ordered assembly of multiprotein complexes ( Hendrick & Hartl 1993, Neuer et al. Originally identified as inducible proteins involved in the protection of cells from multiple stresses, molecular chaperones are now recognized as participants in a diverse range of functions due to their ability to selectively bind to hydrophobic residues of target proteins, directing their involvement in correct protein folding or degradation pathways ( Ellis 1987, Hendrick & Hartl 1993). Further analyses of the intermediary proteins that facilitate the expression of key players in sperm–egg fusion are likely to deliver important insights into this unique event, which culminates in the cytoplasmic continuity of the male and female gametes. Despite these findings, the analysis of oocyte surface multiprotein complexes is currently lacking. Preliminary studies of the oocyte plasma membrane have also revealed the presence of lipid rafts comprising several molecular chaperones, raising the possibility that similar mechanisms may be involved in the activation of maternal fusion machinery and the regulation of oocyte plasma membrane integrity. While the activation of these molecular chaperones and the mechanisms by which they shuttle proteins to the surface of the cell remain the subject of ongoing investigation, a compelling suggestion is that these processes are augmented by dynamic membrane microdomains or lipid rafts that migrate to the apical region of the sperm head after capacitation. Novel research suggests that these highly specific cellular interactions are facilitated by multiprotein complexes that are delivered to and/or assembled on the surface of the gametes by molecular chaperones in preparation for sperm–egg interaction. The remarkable complexity of the molecular events governing adhesion and fusion of the male and female gametes is becoming apparent.
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