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Strain-based sequence variations and structure analysis of murine prostate specific spermine binding protein using
1Department of Biochemistry, Vanderbilt University, Nashville, Tennessee 37232-6400, USA.
Abstract:
Mouse spermine binding protein (SBP) has been characterized using mass spectrometry, including its localization within the prostate, sequence verification, and its posttranslational modifications. MALDI (matrix-assisted laser desorption/ionization) mass spectrometry was employed for localization of proteins expressed by different lobes of the mouse prostate obtained after tissue blotting on a polyethylene membrane. The mass spectra showed complex protein profiles that were different for each lobe of the prostate. The prostate-specific spermine binding protein (SBP), primarily identified by its in-source decay fragment ion signals, was found predominantly expressed by the ventral lobe of the prostate. The MALDI in-source decay measurements combined with nanoESI (nanoelectrospay ionization) MS/MS measurements obtained after specific proteolysis of SBP, allowed the exact positioning of a single N-linked carbohydrate group, and the identification of a pyroglutamate residue at the sequence N-terminus. The N-linked carbohydrate component was further investigated and the general pattern of the N-linked carbohydrate identified. The presence of a disulfide bridge between cysteine78 and cysteine124 was also established. The full sequence characterization of SBP showed several strain-based sequence differences when compared to the published gene sequence.
Insights
Mouse spermine binding protein (SBP) is primarily found in the ventral prostate lobe. Mass spectrometry identified its N-linked glycosylation, N-terminal pyroglutamate, and a disulfide bridge, revealing sequence variations.
Area of Science:
- Proteomics
- Biochemistry
- Mouse models
Background:
- Spermine binding protein (SBP) is a prostate-specific protein.
- Understanding SBP's structure and function is crucial for prostate research.
Purpose of the Study:
- To characterize mouse spermine binding protein (SBP) using mass spectrometry.
- To verify its sequence, identify post-translational modifications, and determine its localization within the mouse prostate.
Main Methods:
- Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry for protein localization via tissue blotting.
- MALDI in-source decay and nanoelectrospray ionization (nanoESI) MS/MS for sequence analysis and post-translational modification identification.
- Proteolytic digestion and peptide mapping for detailed structural characterization.
Main Results:
- SBP is predominantly expressed in the ventral lobe of the mouse prostate.
- Identified a single N-linked carbohydrate group, a pyroglutamate residue at the N-terminus, and a disulfide bridge between Cys78 and Cys124.
- Revealed strain-specific sequence differences in SBP compared to the published gene sequence.
Conclusions:
- Mass spectrometry provides comprehensive characterization of mouse SBP.
- Detailed structural insights into SBP, including post-translational modifications, were obtained.
- Discrepancies between characterized SBP sequence and gene sequence warrant further investigation.