Current biotechnological applications such as biosensors, protein arrays, and microchips require oriented immobilization of enzymes. The characteristics of recognition, self-assembly and ease of genetic manipulation make inorganic binding peptides an ideal molecular tool for site-specific enzyme immobilization. Herein, we demonstrate the utilization of gold binding peptide (GBP1) as a molecular linker genetically fused to alkaline phosphatase (AP) and immobilized on gold substrate. Multiple tandem repeats (n = 5, 6, 7, 9) of gold binding peptide were fused to N-terminus of AP (nGBP1-AP) and the enzymes were expressed in E. coli cells. The binding and enzymatic activities of the bi-functional fusion constructs were analyzed using quartz crystal microbalance spectroscopy and biochemical assays. Among the multiple-repeat constructs, 5GBP1-AP displayed the best bi-functional activity and, therefore, was chosen for self-immobilization studies. Adsorption and assembly properties of the fusion enzyme, 5GBP1-AP, were studied via surface plasmon resonance spectroscopy and atomic force microscopy. We demonstrated self-immobilization of the bi-functional enzyme on micro-patterned substrates where genetically linked 5GBP1-AP displayed higher enzymatic activity per area compared to that of AP. Our results demonstrate the promising use of inorganic binding peptides as site-specific molecular linkers for oriented enzyme immobilization with retained activity. Directed assembly of proteins on solids using genetically fused specific inorganic-binding peptides has a potential utility in a wide range of biosensing and bioconversion processes.

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There is an emerging interest in developing bio-functionalisation routes serving as platforms for assembling diverse enzymes onto material surfaces. Specifically, the fabrication of next-generation, laboratory-on-a-chip-based sensing and energy-harvesting systems requires controlled orientation and organisation of the proteins at the inorganic interfaces. Herein, the authors take the initial steps towards designing multifunctional, enzyme-based platforms by genetically integrating the engineered materialselective peptide tags for tethering redox enzymes onto electrode surfaces. The authors engineered a fusion protein that genetically conjugates gold-binding peptide to formate dehydrogenase derived from Candida methylica. The expressed proteins were tested for both enzyme activity and self-directed gold-surface functionalisation ability. Their findings demonstrate the successful self-immobilisation of the engineered enzyme onto different gold electrodes while retaining the catalytic activity.Building on the functionalisation by the peptides, a fusion enzyme-integrated circuit-based biosensor system was designed. The catalytic conversion of the formate by the engineered dehydrogenase was successfully monitored on the electrode surface at subsequent intervals. The engineered peptide-mediated self-integrated electrode systems can be extended to develop a wide range of biosensing and energy-harvesting platforms using different combinations of materials and biomolecules. This paper contains supporting information that will be made available online once the issue is published. In the meantime, if you wish to get a copy of the supplementary file, please contact the Journals Editor, Sarah Brown, at sarah.brown@icepublishing.com.

AqpZ reconstituted proteoliposomes integrated into polyamide matrix using different ultrafiltration support membranes successfully with a performance increase of 12 times.