Cloning and sequencing of the gene encoding WF146 protease, an extracellular subtilisin-like protease from the thermophile Bacillus sp. WF146, revealed that the WF146 protease was translated as a 416-amino acid precursor consisting of a putative 18-amino acid signal peptide, a 10-kDa N-terminal propeptide and a 32-kDa mature protease region. The mature WF146 protease shares a high degree of amino acid sequence identity with two psychrophilic subtilisins, S41 (68.2%) and S39 (65.4%), and a mesophilic subtilisin, SSII (67.1%). Significantly, these closely related proteases adapted to different temperatures all had four inserted surface loops not found in other subtilisins. However, unlike those of S41, S39 and SSII, the inserted loops of the WF146 protease possessed stabilizing features, such as the introduction of Pro residues into the loop regions. Interestingly, the WF146 protease contained five of the seven mutations previously found in a hyperstable variant of subtilisin S41 obtained by directed evolution. The proform of WF146 protease (pro-WF146 protease) was overexpressed in Escherichia coli in an inactive soluble form. After heat treatment, the 42-kDa pro-WF146 protease converted to a 32-kDa active mature form by processing the N-terminal propeptide. The purified mature WF146 protease hydrolyzed casein with an optimum temperature of 85 ‡C, and lost activity with a half-life of 30 min at 80 ‡C in the presence of 10 mM CaCl 2 .
Purpose To better understand the success of an open source software (OSS) project, this study aims to examine the role of social dependency networks (i.e. social and technical dependencies) in online communities.Design/methodology/approach This study focuses on dependencies using three network metrics – degree centrality, betweenness centrality and closeness centrality – in developer and module networks. A longitudinal analysis from the projects hosted at Sourceforge.net is conducted to examine the effects of social and technical networks on the success of OSS projects. To address our research questions, we have constructed research models to investigate the social network effects in developer networks, the technical network effects in module networks, and the social-technical network effects in both types of networks.Findings The results reveal nonlinear relationships between degree centrality in both social and technical networks and OSS success, highlighting the importance of a moderate level of degree centrality in team structure and software architecture. Meanwhile, a moderate level of betweenness centrality and a lower level of closeness centrality between developers lead to a higher chance of OSS project success.Originality/value This study is the first attempt to consider the network metrics in both module networks of the technical sub-system and developer networks of the social sub-system to better understand their influences on project success.
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