Design of silk proteins with increased heme binding capacity and fabrication of silk-heme materials

• Published in: Journal of inorganic biochemistry Vol. 177; pp. 219 - 227
• Main Authors: Rapson, Trevor D., Liu, Jian-Wei, Sriskantha, Alagacone, Musameh, Mustafa, Dunn, Christopher J., Church, Jeffrey S., Woodhead, Andrea, Warden, Andrew C., Riley, Mark J., Harmer, Jeffrey R., Noble, Christopher J., Sutherland, Tara D.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.12.2017
• Subjects: Coiled coil; De novo protein engineering; EPR; Heme; Honeybee silk; MCD; Honeybee silk; De novo protein engineering; EPR; Heme; Coiled coil; MCD
• ISSN: 0162-0134; 1873-3344
• DOI: 10.1016/j.jinorgbio.2017.08.031

In our previous studies, heme was bound into honeybee silk to generate materials that could function as nitric oxide sensors or as recoverable heterogeneous biocatalysts. In this study, we sought to increase the heme-binding capacity of the silk protein by firstly redesigning the heme binding site to contain histidine as the coordinating residue and secondly, by adding multiple histidine residues within the core of the coiled coil core region of the modified silk protein. We used detergent and a protein denaturant to confirm the importance of the helical structure of the silk for heme coordination. Aqueous methanol treatment, which was used to stabilize the materials, transformed the low-spin, six-coordinate heme to a five-coordinate high-spin complex, thus providing a vacant site for ligand binding. The optimal aqueous methanol treatment time that simultaneously maintains the helical protein structure and stabilizes the silk material without substantial leaching of heme from the system was determined. Design and characterization of a recombinant honeybee silk protein capable of bio-mimetically binding multiple heme. [Display omitted] •Heme binding site in bee silk was redesigned to contain His as coordinating residue.•Strategic introduction of multiple His increased heme binding in silk materials.•Aqueous MeOH transformed bound heme from low spin to 5-coordinate high-spin complex.