A new alkaline serine protease from alkalophilic Bacillus sp.: cloning, sequencing, and characterization of an intracellular protease

An eco-friendly approach of biocontrol of aphid (Aphis gossypii Glover) by Trichoderma harzianum

Aphid (Aphis gossypii) is one of the important pests of papaya crop. In this work, applications of Trichoderma harzianum and Beauveria bassiana (biocontrol agents) and malathion (insecticide) were conducted in vitro and in agrifields for testing their anti-aphid efficacy and compared their efficacy. Furthermore, the enzymatic mechanism of T. harzianum with respect to biocontrolling the pest was unearthed. The LD₅₀ dose of T. harzianum and B. bassiana was 1.2 × 10⁵ spores mL^-1 and 1.0 × 10⁶ spores mL^-1 respectively after 48 h of administration. The LT₅₀ of T. harzianum also exhibited a lower effective time (47.70 h) than B. bassiana (57.53 h) for the same concentration of spores applied (1 × 10⁵ spores mL^-1). The pooled data analysis of two years (2019-2020) showed that the application of T. harzianum spores in agrifields exhibited 31.75 ± 13.00a percentage of reduction of aphid population whereas malathion exhibited 23.93 ± 1.30a%, in comparison to control. The statistical analysis indicated that the application of malathion exhibited the same efficacy as T. harzianum isolate and placed in the same category. In plate detection assay, T. harzianum produced a higher hydrolytic zone for chitinase (8.0 ± 0.4 cm diameter) and protease (7.0 ± 0.4 cm diameter) enzymes, than B. bassiana (1.3 ± 0.2 cm and 1.1 ± 0.2 cm respectively). Quantitative estimation of enzymes exhibited that T. harzianum produced 299 ± 11a μg mL^-1 of chitinase, 519 ± 19a μg mL^-1 of protease, and 65 ± 12a μg mL^-1 of PR1, and on the other hand, B. bassiana yielded 124 ± 12b, 361 ± 23b, and 29 ± 18b μg mL^-1 of chitinase, protease, and PR1 respectively. It indicated that T. harzianum was superior over the B. bassiana in terms of production capacity of all three enzymes. In conclusion, all the above experimental results suggested that T. harzianum showed better aphid-killing efficacy than B. bassiana. It also suggested that T. harzianum should replace hazardous chemical pesticide (malathion) for eco-friendly biocontrol of aphids.

Characterization of an Intracellular Alkaline Serine Protease from Bacillus velezensis SW5 with Fibrinolytic Activity

ISP-SW5 is an intracellular alkaline serine protease gene from Bacillus velezensis SW5 that was heterologously expressed in Escherichia coli BL21 (DE3). Sequence analysis indicated that the ISP-SW5 gene has 960 bp open reading frame and encodes a protein of 319 amino acid residues. Three-dimensional structure of ISP-SW5 with the fibrinolytic activity from Bacillus velezensis was predicted by in silico analysis. Gly219 was the most likely active site for the fibrinolytic activity of ISP-SW5. The recombinant enzyme ISP-SW5 was purified by Ni-NTA Superflow Column. SDS-PAGE showed that this enzyme had a molecular mass of 34 kDa. The result of native-PAGE and N-terminal sequencing showed that the N-terminal propeptide of ISP-SW5 was cleaved during the maturation of protease. The optimum pH and temperature were 8.0 and 40 °C, respectively. Enzyme activity was markedly inhibited by PMSF and EDTA but enhanced by 5 mM Ca²⁺ and 2 mM Zn²⁺ by up to 143% and 115%, respectively. Additionally, ISP-SW5 retained 93%, 78%, and 49% relative enzyme activity after incubation with 0.5 M, 1 M and 2 M NaCl, respectively, at 4 °C for 12 h. The enzyme activity determined by casein as substrate was 1261 U/mg. ISP-SW5 could degrade fibrin at an activity of 3428 U/mg, and its properties reflect its potential application in developing a novel biological catalyst for efficient fibrin hydrolysis in medical treatment.

Mutational analysis of the pro-peptide of a marine intracellular subtilisin protease supports its role in inhibition

Intracellular subtilisin proteases (ISPs) have important roles in protein processing during the stationary phase in bacteria. Their unregulated protein degrading activity may have adverse effects inside a cell, but little is known about their regulatory mechanism. Until now, ISPs have mostly been described from Bacillus species, with structural data from a single homolog. Here, we study a marine ISP originating from a phylogenetically distinct genus, Planococcus sp. The enzyme was successfully overexpressed in E. coli, and is active in presence of calcium, which is thought to have a role in minor, but essential, structural rearrangements needed for catalytic activity. The ISP operates at alkaline pH and at moderate temperatures, and has a corresponding melting temperature around 60 °C. The high-resolution 3-dimensional structure reported here, represents an ISP with an intact catalytic triad albeit in a configuration with an inhibitory pro-peptide bound. The pro-peptide is removed in other homologs, but the removal of the pro-peptide from the Planococcus sp. AW02J18 ISP appears to be different, and possibly involves several steps. A first processing step is described here as the removal of 2 immediate N-terminal residues. Furthermore, the pro-peptide contains a conserved LIPY/F-motif, which was found to be involved in inhibition of the catalytic activity.

Regulation of an intracellular subtilisin protease activity by a short propeptide sequence through an original combined dual mechanism

A distinct class of the biologically important subtilisin family of serine proteases functions exclusively within the cell and forms a major component of the bacilli degradome. However, the mode and mechanism of posttranslational regulation of intracellular protease activity are unknown. Here we describe the role played by a short N-terminal extension prosequence novel amongst the subtilisins that regulates intracellular subtilisin protease (ISP) activity through two distinct modes: active site blocking and catalytic triad rearrangement. The full-length proenzyme (proISP) is inactive until specific proteolytic processing removes the first 18 amino acids that comprise the N-terminal extension, with processing appearing to be performed by ISP itself. A synthetic peptide corresponding to the N-terminal extension behaves as a mixed noncompetitive inhibitor of active ISP with a K(i) of 1 μM. The structure of the processed form has been determined at 2.6 Å resolution and compared with that of the full-length protein, in which the N-terminal extension binds back over the active site. Unique to ISP, a conserved proline introduces a backbone kink that shifts the scissile bond beyond reach of the catalytic serine and in addition the catalytic triad is disrupted. In the processed form, access to the active site is unblocked by removal of the N-terminal extension and the catalytic triad rearranges to a functional conformation. These studies provide a new molecular insight concerning the mechanisms by which subtilisins and protease activity as a whole, especially within the confines of a cell, can be regulated.

Crystal structure of an intracellular subtilisin reveals novel structural features unique to this subtilisin family

The intracellular subtilisin proteases (ISPs) are the only known members of the important and ubiquitous subtilisin family that function exclusively within the cell, constituting a major component of the degradome in many Gram-positive bacteria. The first ISP structure reported herein at a spacing of 1.56 A reveals features unique among subtilisins that has enabled potential functional and physiological roles to be assigned to sequence elements exclusive to the ISPs. Unlike all other subtilisins, ISP from B. clausii is dimeric, with residues from the C terminus making a major contribution to the dimer interface by crossing over to contact the partner subunit. A short N-terminal extension binds back across the active site to provide a potential novel regulatory mechanism of intrinsic proteolytic activity: a proline residue conserved throughout the ISPs introduces a kink in the polypeptide backbone that lifts the target peptide bond out of reach of the catalytic residues.

The IspA protease's involvement in the regulation of the sporulation process of Bacillus thuringiensis is revealed by proteomic analysis

We have observed that the process of sporulation of the ispA-deficient mutant was delayed under phase-contrast microscopy. The protein profiles of the ispA-deficient mutant have been analyzed using two-dimensional gel electrophoresis. The results of a proteomic analysis using MALDI-TOF MS indicated that a sporulation-associated protein, pro- [Formula: see text], was upregulated, while two other sporulation-associated proteins, SpoVD and SpoVR, were downregulated in the ispA-deficient mutant. It has been known that pro- [Formula: see text] is a precursor of [Formula: see text] and is required for gene expression related to the late stage of sporulation. Moreover, SpoVD and SpoVR are known to be involved in the formation of the spore cortex. Based on these observations, we propose that the delay in the sporulation process observed in the ispA-deficient mutant may be due to a failure of [Formula: see text] to signal sporulation. This phenomenon may be further enhanced by insufficient amount of SpoVD and SpoVR for cortex formation. In this study, we have revealed for the first time a possible pathway for the regulation of sporulation-associated proteins via IspA.

Proteolytic activity of cultured Pseudoperkinsus tapetis extracellular products

Several pathogenic protozoan release proteases are necessary for host invasion and initiation of infection. We have identified proteolytic activities in extracellular proteins secreted by the clam parasite Pseudoperkinsus tapetis (Mesomycetozoa) in vitro. The protein concentration of the P. tapetis extracellular products (ECP) increased only during the first week of culture. The appearance of new proteins of 10 and 157 kDa at the second week sample and of 12 kDa at the third week sample was shown by SDS-PAGE. The protease activity rapidly increased in the first 3 weeks of culture, and five clear bands of 23, 29, 60, 67 and 96 kDa with proteolytic activity were detected in the ECP on gelatin SDS-PAGE. Using inhibitors, the proteases were identified as members of the Ca(2+) dependent, serine protease family. Their optimum pH was higher than pH 9.4. The protease activity of the P. tapetis ECP was different than that described for Perkinsus marinus, an oyster pathogen very similar morphologically to the clam parasite and member of the genus in which P. tapetis had been initially included.

Molecular and biotechnological aspects of microbial proteases

Proteases represent the class of enzymes which occupy a pivotal position with respect to their physiological roles as well as their commercial applications. They perform both degradative and synthetic functions. Since they are physiologically necessary for living organisms, proteases occur ubiquitously in a wide diversity of sources such as plants, animals, and microorganisms. Microbes are an attractive source of proteases owing to the limited space required for their cultivation and their ready susceptibility to genetic manipulation. Proteases are divided into exo- and endopeptidases based on their action at or away from the termini, respectively. They are also classified as serine proteases, aspartic proteases, cysteine proteases, and metalloproteases depending on the nature of the functional group at the active site. Proteases play a critical role in many physiological and pathophysiological processes. Based on their classification, four different types of catalytic mechanisms are operative. Proteases find extensive applications in the food and dairy industries. Alkaline proteases hold a great potential for application in the detergent and leather industries due to the increasing trend to develop environmentally friendly technologies. There is a renaissance of interest in using proteolytic enzymes as targets for developing therapeutic agents. Protease genes from several bacteria, fungi, and viruses have been cloned and sequenced with the prime aims of (i) overproduction of the enzyme by gene amplification, (ii) delineation of the role of the enzyme in pathogenecity, and (iii) alteration in enzyme properties to suit its commercial application. Protein engineering techniques have been exploited to obtain proteases which show unique specificity and/or enhanced stability at high temperature or pH or in the presence of detergents and to understand the structure-function relationships of the enzyme. Protein sequences of acidic, alkaline, and neutral proteases from diverse origins have been analyzed with the aim of studying their evolutionary relationships. Despite the extensive research on several aspects of proteases, there is a paucity of knowledge about the roles that govern the diverse specificity of these enzymes. Deciphering these secrets would enable us to exploit proteases for their applications in biotechnology.

Cloning of cellobiose phosphoenolpyruvate-dependent phosphotransferase genes: functional expression in recombinant Escherichia coli and identification of a putative binding region for disaccharides

Genomic libraries from nine cellobiose-metabolizing bacteria were screened for cellobiose utilization. Positive clones were recovered from six libraries, all of which encode phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS) proteins. Clones from Bacillus subtilis, Butyrivibrio fibrisolvens, and Klebsiella oxytoca allowed the growth of recombinant Escherichia coli in cellobiose-M9 minimal medium. The K. oxytoca clone, pLOI1906, exhibited an unusually broad substrate range (cellobiose, arbutin, salicin, and methylumbelliferyl derivatives of glucose, cellobiose, mannose, and xylose) and was sequenced. The insert in this plasmid encoded the carboxy-terminal region of a putative regulatory protein, cellobiose permease (single polypeptide), and phospho-beta-glucosidase, which appear to form an operon (casRAB). Subclones allowed both casA and casB to be expressed independently, as evidenced by in vitro complementation. An analysis of the translated sequences from the EIIC domains of cellobiose, aryl-beta-glucoside, and other disaccharide permeases allowed the identification of a 50-amino-acid conserved region. A disaccharide consensus sequence is proposed for the most conserved segment (13 amino acids), which may represent part of the EIIC active site for binding and phosphorylation.