Background-In the Periodontitis and Vascular Events (PAVE) pilot study, periodontal therapy was provided as an intervention in a secondary cardiac event prevention model through five coordinated cardiac-dental centers.

The human whole saliva proteome was investigated using two-dimensional liquid chromatography (2-DLC). The 2-DLC study was able to identify, with high confidence, 102 proteins including most known salivary proteins (35), and a large number of common serum proteins (67). Peptides from proline-rich proteins, abundant in saliva, had unusual cleavage sites and were frequently only partially tryptic. Three proteins not previously observed in human saliva were also detected. Significantly greater numbers of identified proteins, including high molecular weight, low molecular weight, and proline-rich proteins, were found with 2-DLC compared to previously reported two-dimensional gel electrophoresis studies.

An hemR (hemin-regulated) gene from Porphyromonas gingivalis ATCC 53977 has been isolated and characterized. This gene is present downstream from the prtT gene, previously cloned in this laboratory. In addition, another putative gene, ORF1, was identified between hemR and prtT. The complete nucleotide sequences of ORF1 and hemR were determined, and the deduced amino acid sequence of ORF1 and HemR proteins corresponded to 16-and 48-kDa proteins, respectively. The amino termini of the HemR protein exhibited significant homology with iron-regulated, TonB-dependent outer membrane receptor proteins from various bacteria, while the carboxyl terminus of the HemR protein displayed almost complete identity with a P. gingivalis PrtT protease domain. PCR analyses confirmed the existence of such extensive homology between the carboxyl termini of both the prtT and hemR genes on the P. gingivalis chromosome. Northern blots indicated that ORF1 was part of a 1.0-kb mRNA and was positively regulated by hemin levels. On the other hand, the hemR gene was apparently a part of a 3.0-kb polycistronic message and was negatively regulated at the transcriptional level by hemin. Primer extension analysis of the hemR gene revealed that the transcription start site was at a C residue located within ORF1. An examination of HemR::lacZ constructs in both Escherichia coli and P. gingivalis confirmed hemin repression of hemR expression in both organisms. Moreover, the HemR protein expressed in E. coli was detected by an antiserum from a periodontitis patient heavily colonized with P. gingivalis but not by serum from a periodontally healthy patient or by antisera against hemin-grown P. gingivalis cells. Therefore, it is likely that the 48-kDa HemR protein can be expressed only under heminrestricted conditions. These results suggest that we have isolated a hemin-regulated gene, hemR, which encodes a 48-kDa protein that may be a TonB-dependent outer membrane protein.

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