Biomedical subjects

Karin Scholtmeijer

Publications and source records attributed to Karin Scholtmeijer.

4 recordsLinked to original sources

PubMed2006

Interaction and comparison of a class I hydrophobin from Schizophyllum commune and class II hydrophobins from Trichoderma reesei.

Hydrophobins fulfill a wide spectrum of functions in fungal growth and development. These proteins self-assemble at hydrophilic-hydrophobic interfaces into amphipathic membranes. Hydrophobins are divided into two classes based on their hydropathy patterns and solubility. We show here that the properties of the class II hydrophobins HFBI and HFBII of Trichoderma reesei differ from those of the class I hydrophobin SC3 of Schizophyllum commune. In contrast to SC3, self-assembly of HFBI and HFBII at the water-air interface was neither accompanied by a change in secondary structure nor by a change in ultrastructure. Moreover, maximal lowering of the water surface tension was obtained instantly or took several minutes in the case of HFBII and HFBI, respectively. In contrast, it took several hours in the case of SC3. Oil emulsions prepared with HFBI and SC3 were more stable than those of HFBII, and HFBI and SC3 also interacted more strongly with the hydrophobic Teflon surface making it wettable. Yet, the HFBI coating did not resist treatment with hot detergent, while that of SC3 remained unaffected. Interaction of all the hydrophobins with Teflon was accompanied with a change in the circular dichroism spectra, indicating the formation of an alpha-helical structure. HFBI and HFBII did not affect self-assembly of the class I hydrophobin SC3 of S. commune and vice versa. However, precipitation of SC3 was reduced by the class II hydrophobins, indicating interaction between the assemblies of both classes of hydrophobins.

Air↗

PubMed2005

Hydrophobins: proteins with potential.

Hydrophobins are self-assembling proteins of fungal origin. Their ability to self-assemble into an amphipathic membrane is of interest for many different applications, ranging from medical and technical coatings to the production of proteinaceous glue and cosmetics. Assembled hydrophobins can modify surface characteristics, thus controling the binding properties of the surface; for example, enzymes can be actively and non-covalently immobilized on electrode surfaces and medical coatings can be improved for biocompatibility. Over the past few years research on hydrophobins has contributed to a better understanding of the self-assembly process and is generating more handles to control and manipulate the process. This knowledge could have an immediate effect on production levels, which are not yet adequate, and provide the boost needed for hydrophobins to reach their full potential.

Biocompatible Materials↗

PubMed2004

Highly efficient production of laccase by the basidiomycete Pycnoporus cinnabarinus.

An efficient transformation and expression system was developed for the industrially relevant basidiomycete Pycnoporus cinnabarinus. This was used to transform a laccase-deficient monokaryotic strain with the homologous lac1 laccase gene placed under the regulation of its own promoter or that of the SC3 hydrophobin gene or the glyceraldehyde-3-phosphate dehydrogenase (GPD) gene of Schizophyllum commune. SC3-driven expression resulted in a maximal laccase activity of 107 nkat ml(-1) in liquid shaken cultures. This value was about 1.4 and 1.6 times higher in the cases of the GPD and lac1 promoters, respectively. lac1-driven expression strongly increased when 25 g of ethanol liter(-1) was added to the medium. Accordingly, laccase activity increased to 1,223 nkat ml(-1). These findings agree with the fact that ethanol induces laccase gene expression in some fungi. Remarkably, lac1 mRNA accumulation and laccase activity also strongly increased in the presence of 25 g of ethanol liter(-1) when lac1 was expressed behind the SC3 or GPD promoter. In the latter case, a maximal laccase activity of 1,393 nkat ml(-1) (i.e., 360 mg liter(-1)) was obtained. Laccase production was further increased in transformants expressing lac1 behind its own promoter or that of GPD by growth in the presence of 40 g of ethanol liter(-1). In this case, maximal activities were 3,900 and 4,660 nkat ml(-1), respectively, corresponding to 1 and 1.2 g of laccase per liter and thus representing the highest laccase activities reported for recombinant fungal strains. These results suggest that P. cinnabarinus may be a host of choice for the production of other proteins as well.

Basidiomycota↗

PubMed2002

Surface modifications created by using engineered hydrophobins.

Hydrophobins are small (ca. 100 amino acids) secreted fungal proteins that are characterized by the presence of eight conserved cysteine residues and by a typical hydropathy pattern. Class I hydrophobins self-assemble at hydrophilic-hydrophobic interfaces into highly insoluble amphipathic membranes, thereby changing the nature of surfaces. Hydrophobic surfaces become hydrophilic, while hydrophilic surfaces become hydrophobic. To see whether surface properties of assembled hydrophobins can be changed, 25 N-terminal residues of the mature SC3 hydrophobin were deleted (TrSC3). In addition, the cell-binding domain of fibronectin (RGD) was fused to the N terminus of mature SC3 (RGD-SC3) and TrSC3 (RGD-TrSC3). Self-assembly and surface activity were not affected by these modifications. However, physiochemical properties at the hydrophilic side of the assembled hydrophobin did change. This was demonstrated by a change in wettability and by enhanced growth of fibroblasts on Teflon-coated with RGD-SC3, TrSC3, or RGD-TrSC3 compared to bare Teflon or Teflon coated with SC3. Thus, engineered hydrophobins can be used to functionalize surfaces.

Amino Acid Sequence↗