{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,7]],"date-time":"2026-10-07T02:32:21Z","timestamp":1791340341050,"version":"4.3.1"},"reference-count":70,"publisher":"National Academy of Sciences","issue":"50","content-domain":{"domain":["www.pnas.org"],"crossmark-restriction":true},"short-container-title":["Proc. Natl. Acad. Sci. U.S.A."],"published-print":{"date-parts":[[2006,12,12]]},"abstract":"<jats:p>\n                    Type II protein secretion is critical for\n                    <jats:italic>Legionella pneumophila<\/jats:italic>\n                    infection of amoebae, macrophages, and mice. Previously, we found several enzymes to be secreted by this (Lsp) secretory pathway. To better define the\n                    <jats:italic>L. pneumophila<\/jats:italic>\n                    type II secretome, a 2D electrophoresis proteomic approach was used to compare proteins in wild-type and type II mutant supernatants. We identified 20 proteins that are type II-dependent, including aminopeptidases, an RNase, and chitinase, as well as proteins with no homology to known proteins. Because a chitinase had not been previously reported in\n                    <jats:italic>Legionella<\/jats:italic>\n                    , we determined that wild type secretes activity against both\n                    <jats:italic>p<\/jats:italic>\n                    -nitrophenyl triacetyl chitotriose and glycol chitin. An\n                    <jats:italic>lsp<\/jats:italic>\n                    mutant had a 70\u201375% reduction in activity, confirming the type II dependency of the secreted chitinase. Newly constructed chitinase (\n                    <jats:italic>chiA<\/jats:italic>\n                    ) mutants also had \u224875% less activity, and reintroduction of\n                    <jats:italic>chiA<\/jats:italic>\n                    restored the mutants to normal levels of activity. Although\n                    <jats:italic>chiA<\/jats:italic>\n                    mutants were not impaired for\n                    <jats:italic>in vitro<\/jats:italic>\n                    intracellular infection, they were defective upon intratracheal inoculation into the lungs of A\/J mice, and antibodies against ChiA were detectable in infected animals. In contrast, mutants lacking a secreted phosphatase, protease, or one of several lipolytic enzymes were not defective\n                    <jats:italic>in vivo<\/jats:italic>\n                    . In sum, this study shows that the output of type II secretion is greater in magnitude than previously appreciated and includes previously undescribed proteins. Our data also indicate that an enzyme with chitinase activity can promote infection of a mammalian host.\n                  <\/jats:p>","DOI":"10.1073\/pnas.0608279103","type":"journal-article","created":{"date-parts":[[2006,12,6]],"date-time":"2006-12-06T01:04:16Z","timestamp":1165367056000},"page":"19146-19151","update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":209,"title":["<i>Legionella pneumophila<\/i>\n                    type II secretome reveals unique exoproteins and a chitinase that promotes bacterial persistence in the lung"],"prefix":"10.1073","volume":"103","author":[{"given":"Sruti","family":"DebRoy","sequence":"first","affiliation":[{"name":"Department of Microbiology\u2013Immunology, Northwestern University Medical School, Chicago, IL 60611"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jenny","family":"Dao","sequence":"additional","affiliation":[{"name":"Department of Microbiology\u2013Immunology, 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