PROTEINS IN THE ORAL FLUIDS AND TOOTH PELLICLE LAYER

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The acquired enamel pellicle is the organic film primarily derived from salivary components that covers and protects the enamel surface of teeth. The ultimate aim of this project is to characterize the composition and functional properties of the acquired enamel pellicle. Previous studies, using methods including gel electrophoresis, classical protein separation chromatography, and antibody detection were limited by the small amounts of material. These methods suggested that the pellicle is composed of one component or another in amounts difficult to relate to the pellicle as a whole. Past efforts, in particular adsorption studies using radiolabelled proteins and mass spectral analysis of pellicle proteins separated by 2-D PAGE, provided information indicating a high content of phosphorylated proteins. Additionally, proline-rich proteins, statherin and cystatin SN, were identified in artificial pellicles produced by adsorption of salivary secretions to hydroxyapatite. However, when a similar analysis of proteins derived from in vivo collected pellicle was conducted, the proline-rich proteins were notably absent. Characterization of 2D gel spots from saliva and in vivo pellicle was performed by analyzing extracted tryptic peptides. Database searches using both MS and MS/MS data obtained using MALDI-TOF and Q-oTOF MS identified expected salivary proteins (cystatins, amylase, statherin, and others), as well as unanticipated gingival serum fluid proteins (i.e., calgranulin) and cellular proteins (endothelial keratins). Our results from this study were published in J. Biol. Chem. In order to provide an even more comprehensive picture of salivary and pellicle components, ion exchange chromatography coupled with on-line capillary LC/MS has been employed. To facilitate this analysis, a defined database containing all the known oral proteins and other components that can be present in the oral cavity has been constructed and the resuls from the salivary proeome study are being consulted. Data acquired during intelligent data acquisition (IDA) operation of the capLC-QStar i nanoESI-orthogonal TOF MS system can be quickly searched against the available databases, and searches that allow for all known post-translational modifications can be performed rapidly and reliably. Use of this approach has significantly increased the assignments of eluting peaks and has yielded highly reliable and consistently relevant results. This approach should lead to an in-depth understanding of protein synthesis/degradation pathways and functions in oral fluids and human pellicle. Prof. Oppenheim's department recently acquired its own LTQ MS in order to dedicate more time to these analyses. Resource personnel will continue to provide advice and consultation.