Archetypes of open-source business models

Electronic Markets - The open-source paradigm offers a plethora of opportunities for innovative business models (BMs) as the underlying codebase of the technology is accessible and extendable by...     

The active sites of the eukaryotic 20 S proteasome and their involvement in subunit precursor processing

The 26 S proteasome is the central protease involved in ubiquitin-mediated protein degradation and fulfills vital regulatory functions in eukaryotes. The proteolytic core of the complex is the 20 S proteasome, a cylindrical particle with two outer rings each made of 7 different alpha-type subunits and two inner rings made of 7 different beta-type subunits. In the archaebacterial 20 S proteasome ancestor proteolytically active sites reside in the 14 uniform beta-subunits. Their N-terminal threonine residues, released by precursor processing, perform the nucleophilic attack for peptide bond hydrolysis. By directed mutational analysis of 20 S proteasomal beta-type proteins of Saccharomyces cerevisiae, we identified three active site-carrying subunits responsible for different peptidolytic activities as follows: Pre3 for post-glutamyl hydrolyzing, Pup1 for trypsin-like, and Pre2 for chymotrypsin-like activity. Double mutants harboring only trypsin-like or chymotrypsin-like activity were viable. Mutation of two potentially active site threonine residues in the Pre4 subunit excluded its catalytic involvement in any of the three peptidase activities. The generation of different, incompletely processed forms of the Pre4 precursor in active site mutants suggested that maturation of non-active proteasomal beta-type subunits is exerted by active subunits and occurs in the fully assembled particle. This trans-acting proteolytic activity might also account for processing intermediates of the active site mutated Pre2 subunit, which was unable to undergo autocatalytic maturation.     

Designing business model taxonomies – synthesis and guidance from information systems research

Classification is an essential approach in business model research. Empirical classifications, termed taxonomies, are widespread in and beyond Information Systems (IS) and enjoy high popularity as both stand-alone artifacts and the foundation for further application. In this article, we focus on the study of empirical business model taxonomies for two reasons. Firstly, as these taxonomies serve as a tool to store empirical data about business models, we investigate their coverage of different industries and technologies. Secondly, as they are emerging artifacts in IS research, we aim to strengthen rigor in their design by illustrating essential design dimensions and characteristics. In doing this, we contribute to research and practice by synthesizing the diffusion of business model taxonomies that helps to draw on the available body of empirical knowledge and providing artifact-specific guidance for building taxonomies in the context of business models.

     

Enhanced recovery and purification of Aspergillus glucoamylase from Saccharomyces cerevisiae by the addition of poly(aspartic acid) tails

Poly(aspartic acid) tails of different lengths were fused to the glucoamylase (GA) of Aspergillus awamori by genetic engineering techniques. Tails consisting of 5, 7, and 10 aspartate residues were fused to the N-terminus of the full-length mature GA (aa 1-616) downstream from the intact leader peptide to produce fusion proteins designated GAND5, GAND7, and GAND10, respectively. Three fusion proteins with C-terminal tails were also constructed, designated GACD0, GACD5, and GACD10 (0, 5, and 10 aspartate residues, respectively). For the C-terminal fusion proteins, the tails were fused to a catalytically active but truncated form of GA (aa 1-484). All of the charged tails had the general sequence Met-Ala-Aspn-Tyr, where n = 0, 5, 7, or 10. The modified genes were expressed in the yeast Saccharomyces cerevisiae and the proteins secreted into the culture medium. The enzymes were subsequently purified by affinity chromatography. The specific activity of each purified enzyme was found to be comparable to the wild-type enzyme. The C-terminal tails did not interfere with expression, whereas decreased extracellular glucoamylase activities corresponding to increased tail length were found for the N-terminal fusion proteins. Amino-terminal amino acid sequence analysis of the purified GAND proteins confirmed the authenticity of the amino termini of the modified proteins and showed that both the leader peptidase and KEX2 protease cleavages had occurred faithfully. The increased net negative charge of the GAND and GACD proteins was indicated by both nondenaturing PAGE and isoelectric focusing.(ABSTRACT TRUNCATED AT 250 WORDS)