Purpose: To investigate the accumulation of TGFBIp in GCDIII and to demonstrate the ability to perform mass spectrometry on old two-dimensional protein gels.
Methods: Proteins were extracted from one cornea with GCDIII from a person with an Arg124Leu mutation in the TGFBI (BIGH3) gene and from one normal human cornea in 1987 and subjected to two-dimensional (2D) gel electrophoresis. After keeping the gels at room temperature for 15 years, protein spots of interest were excised and digested with trypsin. The tryptic-derived peptides were analyzed using mass spectrometry.
Results: Four areas of interest were examined and four different proteins (TGFBIp, aldehyde dehydrogenase class 3, actin, and albumin) were identified in the 15-year-old gels. Using image analysis, the amount of TGFBIp was found to be 77 fold higher in the GCDIII affected cornea relative to the normal tissue. In both situations, TGFBIp migrated on the 2D gels as a 63 kDa protein. Mass spectrometry revealed the same nine peptides in TGFBIp from both the normal and the GCDIII affected corneas, including one peptide situated at the amino terminus. Moreover, the cornea with GCDIII contained abundant 40 kDa TGFBIp fragments that were lacking sequences in both the amino and carboxy termini.
Conclusions: Mass spectrometry can be performed on old 2D polyacrylamide gels. In both normal and GCDIII affected corneas, the majority of TGFBIp migrated on 2D gels as a 63 kDa protein with an intact amino terminus. However, the amount of the 63 kDa TGFBIp was 77 fold higher in the GCDIII affected cornea. Furthermore, the GCDIII affected cornea contained abundant 40 kDa fragments that were trunctated in both the amino and carboxy termini.