Mutational analysis of the first 15 amino acid residues of the UL51 protein. (A) The first 15 amino acids of UL51w/t were fused to the N terminus of GFP in frame (UL51N15GFP). U251 cells were transfected with pEGFP-N3 (panels a to c) or UL51N15GFP (d to f). At 24 h posttransfection, the cells were fixed and permeabilized as described in Materials and Methods. The samples were reacted with anti-Golgi-58K protein mouse monoclonal antibody (panels b and e). The inset shows high magnification of the juxtanuclear region. (B) The cysteine at position 9 of UL51w/t was replaced by serine (UL51C9S) or alanine (UL51C9A). U251 cells were transfected with UL51w/t (panels a to c), UL51C9S (panels d to f), or UL51C9A (panels g to i). The samples were double stained with anti-UL51 rabbit polyclonal antibody (panels a, d, and g) and anti-Golgi-58K protein mouse monoclonal antibody (panels b, e, and h). Fluorescence images were obtained with the Bio-Rad MRC 1024 confocal imaging system.