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The C‐terminal domains of the gingipain K polyprotein are necessary for assembly of the active enzyme and expression of associated activities
Author(s) -
Sztukowska Maryta,
Sroka Aneta,
Bugno Marcin,
Banbula Agnieszka,
Takahashi Yusuke,
Pike Robert N.,
Genco Caroline A.,
Travis James,
Potempa Jan
Publication year - 2004
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2004.04357.x
Subject(s) - porphyromonas gingivalis , biology , mutant , microbiology and biotechnology , western blot , c terminus , gene , biochemistry , genetics , amino acid , bacteria
Summary The Porphyromonas gingivalis lysine‐specific cysteine protease (gingipain K, Kgp) is expressed as a large precursor protein consisting of a leader sequence, a pro‐fragment, a catalytic domain with a C‐terminal IgG‐like subdomain (IgSF) and a large haemagglutinin/adhesion (HA) domain. In order to directly study the role of these non‐catalytic domains in pro‐Kgp processing and maturation in P. gingivalis , the wild‐type form of the gene was replaced with deletion variants encoding C‐terminally truncated proteins, including KgpΔHA3/4 (Δ1292–1732 aa), KgpΔHA2‐4 (Δ1157–1732 aa), KgpΔHA1‐4 (Δ738–1732 aa), KgpΔC‐term/HA (Δ681–1732 aa) and KgpΔIg/C‐term/HA (602–1732 aa). Northern blot and reverse transcription polymerase chain reaction (RT‐PCR) analysis revealed that all truncated variants of the kgp gene were transcribed in P. gingivalis . Despite high levels of kgp ΔC‐term/HA and kgp ΔIg/C‐term/HA transcripts, no Kgp‐specific antigen was detected in cultures of these mutants as determined by Western blot analysis with monoclonal antibodies specific for the Kgp catalytic domain. Furthermore, only barely measurable amounts of Kgp‐specific activity were detected in these two mutants. The remaining mutants expressed significant Kgp activity, however, at lower levels when compared with the parental strain. The decreased activity most probably resulted from altered folding and/or hindered secretion of the protein. The kgp gene truncation was also demonstrated to alter the distribution of the gingipain protein between membrane‐associated and ‐secreted forms. While both gingipain K activity and the protein were cell membrane‐associated in the parental strain, the mutants released significant amounts of both protein and activity into the media. Taken together, these results suggest that the C‐terminal HA domains of Kgp are not only essential for full expression of gingipain activity, but also for proper processing of the multiprotein complex assembly on the P. gingivalis outer membrane. Moreover, our results indicate that the immunoglobulin‐like subdomain is indispensable for proper folding and expression of the gingipains.