Heat stable proteinase from Thermomonospora fusca. Characterization as a serine proteinase

Proteomic and transcriptomic analysis of extracellular proteins and mRNA levels in Thermobifida fusca grown on cellobiose and glucose

Thermobifida fusca secretes proteins that carry out plant cell wall degradation. Using two-dimensional electrophoresis, the extracellular proteome of T. fusca grown on cellobiose was compared to that of cells grown on glucose. Extracellular proteins, the expression of which is induced by cellobiose, mainly are cellulases and cellulose-binding proteins. Other major extracellular proteins induced by cellobiose include a xylanase (Xyl10A) and two unknown proteins, the C-terminal regions of which are homologous to a lytic transglycosylase goose egg white lysozyme domain and an NLPC_P60 domain (which defines a family of cell wall peptidases), respectively. Transcriptional analysis of genes encoding cellobiose-induced proteins suggests that their expression is controlled at the transcriptional level and that their expression also is induced by cellulose. Some other major extracellular proteins produced by T. fusca grown on both cellobiose and glucose include Lam81A and three unknown proteins that are homologous to aminopeptidases and xylanases or that contain a putative NLPC_P60 domain.

Mesophile versus thermophile: insights into the structural mechanisms of kinetic stability

Obtaining detailed knowledge of folding intermediate and transition state (TS) structures is critical for understanding protein folding mechanisms. Comparisons between proteins adapted to survive extreme temperatures with their mesophilic homologs are likely to provide valuable information on the interactions relevant to the unfolding transition. For kinetically stable proteins such as alpha-lytic protease (alphaLP) and its family members, their large free energy barrier to unfolding is central to their biological function. To gain new insights into the mechanisms that underlie kinetic stability, we have determined the structure and high temperature unfolding kinetics of a thermophilic homolog, Thermobifida fusca protease A (TFPA). These studies led to the identification of a specific structural element bridging the N and C-terminal domains of the protease (the "domain bridge") proposed to be associated with the enhanced high temperature kinetic stability in TFPA. Mutagenesis experiments exchanging the TFPA domain bridge into alphaLP validate this hypothesis and illustrate key structural details that contribute to TFPA's increased kinetic thermostability. These results lead to an updated model for the unfolding transition state structure for this important class of proteases in which domain bridge undocking and unfolding occurs at or before the TS. The domain bridge appears to be a structural element that can modulate the degree of kinetic stability of the different members of this class of proteases.

Expression and characterization of a thermostable serine protease (TfpA) from Thermomonospora fusca YX in Pichia pastoris

A serine protease produced by Thermomonospora fusca YX (TfpA) is heat-stable (up to 85 degrees C) and has a broad pH activity range and strong resistance to detergents. The objective of this study was to determine if the methylotropic yeast Pichia pastoris could express TfpA extracellularly. A 1.0-kb DNA fragment (tfpA) encoding the pro-peptide and mature protein of TfpA was cloned into expression vectors pPICZalphaA (inducible) and pGAPZalphaA (constitutive) and introduced into P. pastoris by electroporation. Expression of r-TfpA was greater in the inducible system than in the constitutive one, producing 135 U ml(-1) medium supernatant 6 days after methanol induction. The r-TfpA was not glycosylated (21.7 kDa), and had pH and temperature optima of 8.5 and 80 degrees C, respectively, using azocasein as a substrate. In conclusion, P. pastoris can be used as a host to produce extracellular r-TfpA, and expression efficiency may be improved by optimizing fermentation conditions and modifying factors related to protein expression and stability.

Cloning, sequencing, and expression of a Thermomonospora fusca protease gene in Streptomyces lividans

The major Thermomonospora fusca YX extracellular protease gene (tfpA) was cloned into Escherichia coli and Streptomyces lividans and was sequenced. The open reading frame encoded 375 residues, including a 31-residue potential signal sequence, an N-terminal prosequence containing 150 residues, and the 194-residue mature protease that belongs to the chymotrypsin family. The protease was secreted by S. lividans, but evidence suggested that it was bound to an extracellular protease inhibitor. An inhibitor-deficient mutant was selected to produce protease for purification.