Insertion of a chaperone domain converts FKBP12 into a powerful catalyst of protein folding.
The catalytic activity of human FKBP12 as a prolyl isomerase is high towards short peptides, but very low in proline-limited protein folding reactions. In contrast, the SlyD proteins, which are members of the FKBP family, are highly active as folding enzymes. They contain an extra "insert-in-flap" or IF domain near the prolyl isomerase active site. The excision of this domain did not affect the prolyl isomerase activity of SlyD from Escherichia coli towards short peptide substrates but abolished its catalytic activity in proline-limited protein folding reactions. The reciprocal insertion of the IF domain of SlyD into human FKBP12 increased its folding activity 200-fold and generated a folding catalyst that is more active than SlyD itself. The IF domain binds to refolding protein chains and thus functions as a chaperone module. A prolyl isomerase catalytic site and a separate chaperone site with an adapted affinity for refolding protein chains are the key elements for a productive coupling between the catalysis of prolyl isomerization and conformational folding in the enzymatic mechanisms of SlyD and other prolyl isomerases, such as trigger factor and FkpA.
Knappe
Thomas A
TA
Laboratorium für Biochemie, Universität Bayreuth, D-95440 Bayreuth, Germany.
Eckert
Barbara
B
Schaarschmidt
Peter
P
Scholz
Christian
C
Schmid
Franz X
FX
D000595:Amino Acid Sequence; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D019696:Peptidylprolyl Isomerase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011392:Proline / Q000378:metabolism; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D022061:Tacrolimus Binding Protein 1A / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; D011993:Recombinant Fusion Proteins; C085606:SlyD protein, E coli; D011392:Proline; D022061:Tacrolimus Binding Protein 1A; D019696:Peptidylprolyl Isomerase