FIG. 6.

Mass spectrometric analysis of purified KSHV virion proteins. (A) Purified virion lysate was revolved on a 4 to 12% Bis-Tris NuPAGE gel with MOPS running buffer and stained by using a silver staining kit (Amersham). The band which was suspected to be ORF45 is indicated. The numbers on the right indicate molecular masses (in kilodaltons) of protein markers. (B) The purified virions were precipitated with TCA, and the proteins were resolved on a NuPAGE gel as in panel A. The gel was stained with colloidal Coomassie G-250. The suspected ORF45 band and the band above were excised and subjected to mass spectrometry analysis. The resultant MS/MS spectra were run against a sequence database by using the SEQUEST program. Three peptide sequences (among them one was a partially digested peptide and shares overlap sequence with another peptide) were identified which matched KSHV ORF45 (C). The identified proteolytic peptide fragments in the ORF45 sequence are shown in boldface type in panel B.