Structure-function analysis of PrsA reveals roles for the parvulin-like and flanking N- and C-terminal domains in protein folding and secretion in Bacillus subtilis

: Vitikainen M, Lappalainen I, Seppala R, Antelmann H, Boer H, Taira S, Savilahti H, Hecker M, Vihinen M, Sarvas M, Kontinen VP

Publisher: AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

: 2004

JOURNAL OF BIOLOGICAL CHEMISTRY

: J BIOL CHEM

: 279

: 18

: 19302

: 19314

: 13

: 0021-9258

DOI: https://doi.org/10.1074/jbc.M400861200

The PrsA protein of Bacillus subtilis is an essential membrane-bound lipoprotein that is assumed to assist post-translocational folding of exported proteins and stabilize them in the compartment between the cytoplasmic membrane and cell wall. This folding activity is consistent with the homology of a segment of PrsA with parvulin-type peptidyl-prolyl cis/trans isomerases (PPIase). In this study, molecular modeling showed that the parvulin-like region can adopt a parvulin-type fold with structurally conserved active site residues. PrsA exhibits PPIase activity in a manner dependent on the parvulin-like domain. We constructed deletion, peptide insertion, and amino acid substitution mutations and demonstrated that the parvulin-like domain as well as flanking N- and C-terminal domains are essential for in vivo PrsA function in protein secretion and growth. Surprisingly, none of the predicted active site residues of the parvulin-like domain was essential for growth and protein secretion, although several active site mutations reduced or abolished the PPIase activity or the ability of PrsA to catalyze proline-limited protein folding in vitro. Our results indicate that PrsA is a PPIase, but the essential role in vivo seems to depend on some non-PPIase activity of both the parvulin-like and flanking domains.