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A homodimer represents an active species of the peptidyl‐prolyl cis/trans isomerase FKBP25mem from Legionella pneumophila
Author(s) -
Schmidt Bettina,
Rahfeld Jens,
Schierhorn Angelika,
Ludwig Birgit,
Hacker Jörg,
Fischer Gunter
Publication year - 1994
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(94)00970-8
Subject(s) - legionella pneumophila , dimer , isomerase , molecular mass , peptidylprolyl isomerase , cis trans isomerases , fkbp , chemistry , enzyme , biochemistry , recombinant dna , prolyl isomerase , monomer , stereochemistry , biology , bacteria , pin1 , genetics , organic chemistry , gene , polymer
The molecular mass of the native FK506‐binding peptidyl‐prolyl cis/trans isomerase (PPIase) FKBP25mem from Legionella pneumophila (Mip (macrophage infectivity potentiator) protein) was determined by two methods. By gel‐permeation chromatography we found no indication of the presence of the monomeric enzyme. However, an oligomeric state with a molecular mass of about 62 kDa was detected. By cross‐linking with dimethyl pimelimidate and subsequent SDS‐PAGE of either the surface proteins of intact L. pneumophila cells or the purified recombinant FKBP25mem in solution, we observed an immunoreactive band indicative of a mass in the dimer range. In contrast to human recombinant FKBP12, the enzymatic activity of Legionella FKBP25mem was strongly dependent on the protein concentration, pointing to a dimer as the most active species. However, the inhibition by FK506 yielded a nearly constant value of K i of about 250 nM when measured in the same range of FKBP25mem concentration. These results may be explained by the fact that monomeric FKBP25mem has little, if any, influence on enzymatic activity when compared with the homodimer.