Protease-deficient Bacillus subtilis host strains for production of Staphylococcal protein A.

We constructed strains of Bacillus subtilis which produced very low levels of extracellular proteases. These strains carried insertion or deletion mutations in the subtilisin structural gene (apr) which were constructed in vitro by using the cloned gene. The methods used to construct the mutations involved the use of a plasmid vector which allowed the selection of chromosomal integrates and their subsequent excision by homologous recombination to effect replacement of the chromosomal apr gene by a derivative carrying an inactivating insert with a selectable marker (a cat gene conferring chloramphenicol resistance). The strains produced no subtilisin, no detectable extracellular metalloprotease activity, and residual extracellular serine protease levels as low as 0.5% of that of the standard strain from which they were derived. The strains proved to be superior host strains for the production of staphylococcal protein A, accumulating higher levels of intact protein than do previously available B. subtilis strains.     

Gene for an immunoglobulin-binding protein from a group G streptococcus.

The gene (spg) for an immunoglobulin G (IgG)-binding protein from a Streptococcus clinical isolate of Lancefield group G was cloned and expressed in Escherichia coli. The complete nucleotide sequence of the gene and 5'-flanking sequences was determined. The DNA sequence includes an open reading frame which encodes a hypothetical protein of 448 amino acid residues (Mr = 47,595). The 5' end of this open reading frame encodes a sequence resembling a typical secretion signal sequence, and the remainder of the encoded protein has features reminiscent of staphylococcal protein A and of streptococcal M6 protein, including repeated sequences and a similar C-terminal structure. Aside from this C-terminal structure, the encoded protein has little direct amino acid sequence homology to either protein A or M6 protein. In E. coli, the cloned gene directs the synthesis of a protein which binds to immunoglobulins, including rabbit immunoglobulin, goat IgG, and human IgG3(lambda). Its binding properties are similar to those of the protein G described by Bj?rck and Kronvall (L. Bj?rck and G. Kronvall, J. Immunol. 133:969-974, 1984), a type III Fc receptor from a group G streptococcus.     

Identification of homologues of a functionally important 50 S ribosomal protein in different bacterial species.

Functional homology between the 50 S ribosomal protein L3 from Bacillus stearothermophilus and a protein from each of three other species of Bacillaceae (Bacillus licheniformis, Bacillus megaterium, and Bacillus subtilis) is demonstrated by substituting each of the proteins for B. stearothermophilus L3 in active reconstituted ribosomes. The structurally related protein from Escherichia coli, L2, cannot replace B, stearothermophilus L3, nor can any other E. coli protein.     

Computational and experimental investigation of flow and particle settling in a roller bottle bioreactor

It is shown that cell settling is a key factor affecting the performance of roller bottle bioreactors. The two-dimensional cross-sectional flow at the center of a roller bottle is simulated using a finite difference method, and the settling behavior of cells is simulated using particle dynamics algorithms and validated experimentally using fluorescent particles. The settling behavior of particles in the roller bottle flow is studied using both steady and time dependent rotation rates. Under steady flow conditions the flow is divided into two regions: one where the particles settle to the wall and one where the particles remain suspended indefinitely. The relative size of these two regions depends on the ratio of the settling velocity to the rotation rate of the bottle. For unsteady flows generated by periodic changes of the bottle rotation direction, the settling of cells is accelerated significantly, leading to complete deposition in just a few turns of the bottle.     

Production and purification of recombinant DP1B silk-like protein in plants

Spider dragline silk of Nephila clavipes consists of two highly repetitive proteins, spidroin 1 and spidroin 2. To develop a plant platform for production of recombinant silk-like protein, two plant-optimized DP1B genes were synthesized to mimic spidroin 1. DP1B-8P encodes for a 64 kD DP1B silk-like protein and DP1B-16P for a 127 kD DP1B silk-like protein. Both genes have been introduced into Arabidopsis for leaf-based production driven by the 35S promoter and for seed-specific production driven by the -conglycinin subunit promoter, respectively. They have also been expressed in somatic soybean embryos under the control of the -conglycinin subunit promoter. The results demonstrate the synthesis and accumulation of DP1B silk-like protein in leaves and seeds of Arabidopsis, as well as in somatic soybean embryos. They suggest that seeds are the more preferred tissue for DP1B production since they offer higher production yield and quality. In addition, a simplified protocol for purifying DP1B from plant tissue is discussed.     

High yield recombinant silk-like protein production in transgenic plants through protein targeting

DP1B is a synthetic analogue of spider dragline silk protein. It can be spun to form silk fiber. Previously, it had been expressed in transgenic plants, showing the general feasibility of the plant-based DP1B production. However, success of such a plant-based platform requires a great increase of DP1B productivity in plant cells to reduce production cost. This report describes a protein targeting approach to accumulate DP1B in apoplast, ER lumen, and vacuole in Arabidopsis cells, by utilizing appropriate combinations of sporamin-targeting determinant peptides and ER retention peptide. The approach has dramatically enhanced DP1B accumulation, resulting in high production yield. The accumulation can be as high as 8.5 and 6.7% total soluble protein in leaf tissue by targeting to apoplast and ER lumen, respectively, or as high as 18 and 8.2% total soluble protein in seeds by targeting to ER lumen and vacuole, respectively. However, the vacuole targeting in leaves and the apoplast targeting in seeds have failed to accumulate full length DP1B molecules or any DP1B at all, respectively, suggesting that they may not be suitable for applications in leaf tissues and seeds. Data in this study recommend a combination of seed-specific expression and ER-targeting as one of the best strategies for yield enhancement of plant-based DP1B production.     

The nerve growth factor precursor proNGF exhibits neurotrophic activity but is less active than mature nerve growth factor

Nerve growth factor (NGF) promotes neuronal survival and differentiation and stimulates neurite outgrowth. NGF is synthesized as a precursor, proNGF, which undergoes post-translational processing to generate mature beta-NGF. It has been assumed that, in vivo, NGF is largely processed into the mature form and that mature NGF accounts for the biological activity. However, we recently showed that proNGF is abundant in CNS tissues whereas mature NGF is undetectable, suggesting that proNGF has biological functions beyond its role as a precursor. To determine whether proNGF exhibits biological activity, we mutagenized the precursor-processing site and expressed unprocessed, cleavage-resistant proNGF protein in insect cells. Survival and neurite outgrowth assays on murine superior cervical ganglion neurons and PC12 cells indicated that proNGF exhibits neurotrophic activity similar to mature 2.5S NGF, but is approximately fivefold less active. ProNGF binds to the high-affinity receptor, TrkA, as determined by cross-linking to PC12 cells, and is also slightly less active than mature NGF in promoting phosphorylation of TrkA and its downstream signaling effectors, Erk1/2, in PC12 and NIH3T3-TrkA cells. These data, coupled with our previous report that proNGF is the major form of NGF in the CNS, suggest that proNGF could be responsible for much of the biological activity normally attributed to mature NGF in vivo.     

Differential nuclear localization of the major adenovirus type 2 E1a proteins.

The localization in infected and transformed cells of the two major adenovirus type 2 E1a proteins, of 289 and 243 amino acid residues, was studied with antisera raised against synthetic peptides or a TrpE-E1a fusion protein. Both E1a proteins were detected only in the nucleus of infected cells as determined by immunofluorescence analysis of cells infected with wild-type virus or with the mutants pm975 or dl1500, which produce, respectively, only the 289-residue or only the 243-residue E1a protein. However, the 289-residue protein was more tightly associated with the nucleus than was the 243-residue protein, as determined by the stability of nuclear fluorescence to different fixation procedures and by the use of radioimmunoprecipitation and Western blot analysis to analyze fractions extracted from the nucleus by detergent and other treatments. The latter experiments revealed that only the 289-residue protein, and only a fraction of that protein present in the nucleus, is associated with the nuclear matrix, both in infected HeLa cells and in the transformed human cell line 293.     

The sequence of a cDNA clone coding for a novel kallikrein from mouse submaxillary gland.

Mouse submaxillary gland contains many proteolytic enzymes, the most widely studied of which are the kallikreins. This gland also contains high levels of nerve growth factor (NGF), which is isolated as a complex of three subunits, alpha, beta, and gamma. We report here the cloning and sequence analysis of a novel kallikrein from mouse submaxillary gland. Antibodies directed against the alpha subunit precipitate the product of this clone, but do not precipitate the homologous gamma subunit. This new kallikrein is therefore closely related to alpha NGF, yet in contrast to the alpha subunit, its sequence suggests it has proteolytic activity.     

beta-NGF-endopeptidase: structure and activity of a kallikrein encoded by the gene mGK-22

Mouse nerve growth factor (NGF) is cleaved at a histidine-methionine bond to release an NH2-terminal octapeptide (NGF1-8). The enzyme responsible, beta-NGF-endopeptidase, is structurally and functionally similar to gamma-NGF and epidermal growth factor-binding protein (EGF-BP) and cleaves mouse low molecular weight kininogen to produce bradykinin-like activity. These data have suggested that, like gamma-NGF and EGF-BP, beta-NGF-endopeptidase is a mouse glandular kallikrein. Evidence for a physiological role for NGF1-8 encouraged studies to further characterize the structure and function of this enzyme. Purified beta-NGF-endopeptidase migrated as a single band on isoelectric focusing and reducing SDS-polyacrylamide gels. As was expected, it removed NGF1-8 from NGF. Interestingly, enzymatic activity on an artificial substrate, and on NGF, was inhibited by NGF1-8 and by bradykinin. These studies further supported the view that beta-NGF-endopeptidase acts on both NGF and kininogen. The first 30 NH2-terminal amino acids of beta-NGF-endopeptidase were sequenced. This analysis demonstrated that the enzyme is encoded by the gene designated mGK-22 (Evans et al., 1987). The sequence of this gene corresponds to that of EGF-BP type A (Anundi et al., 1982; Drinkwater et al., 1987), and so studies were performed to determine whether or not beta-NGF-endopeptidase participates in EGF complex formation. Chromatographic and kinetic data gave no evidence that beta-NGF-endopeptidase is an EGF-binding protein. Our studies suggest that contamination of high molecular weight (HMW) EGF preparations with beta-NGF-endopeptidase erroneously led to earlier designation of the product of mGK-22 as an EGF-BP.(ABSTRACT TRUNCATED AT 250 WORDS)