Article Bacterial Proteins Gene Expression Regulation, Bacterial PG1659 protein Porphyromonas gingivalis Sigma Factor Stress, Physiological Virulence amino terminal sequence anti-sigma factor bacterial protein bacterial strain controlled study cytoplasm gene expression regulation genetics membrane protein metabolism nonhuman oxidative stress physiological stress protein function protein protein interaction sigma factor sigma factor RpoE two hybrid system unclassified drug upregulation virulence wild type