FIGURE 3.

gB endodomain harbors a palmitoylated cysteine residue. A, schematic diagram of HCMV gB protomer (sp, signal peptide; TM, transmembrane helix). The close-up shows the juxtamembrane and TM amino acid sequence alignment from different HCMV strains (see Footnote 3) with the endodomain Cys residue highlighted; due to two polymorphic sites in the gB ectodomain, residue numbering differs slightly among the four strains. The Cys-777 position number refers to the VR1814 gB allele used in this study. B, acyl-biotinyl exchange assay on purified gB and gB_C777A as described under “Experimental Procedures.” Hydroxylamine (HAM) was omitted in a series of samples as a control. Eluted proteins were probed in immunoblot (IB) with anti-biotin to detect labeled Cys residues or anti-gB antibody to verify the equal loading.