title: Rational design of a zinc phthalocyanine binding protein.
abstract: Phthalocyanines have long been used as primary donor molecules in synthetic light-powered devices due to their superior properties when compared to natural light activated molecules such as chlorophylls. Their use in biological contexts, however, has been severely restricted due to their high degree of self-association, and its attendant photoquenching, in aqueous environments. To this end we report the rational redesign of a de novo four helix bundle di-heme binding protein into a heme and Zinc(II) phthalocyanine (ZnPc) dyad in which the ZnPc is electronically and photonically isolated. The redesign required transformation of the homodimeric protein into a single chain four helix bundle and the addition of a negatively charge sulfonate ion to the ZnPc macrocycle. To explore the role of topology on ZnPc binding two constructs were made and the resulting differences in affinity can be explained by steric interference of the newly added connecting loop. Singular binding of ZnPc was verified by absorption, fluorescence, and magnetic circular dichroism spectroscopy. The engineering guidelines determined here, which enable the simple insertion of a monomeric ZnPc binding site into an artificial helical bundle, are a robust starting point for the creation of functional photoactive nanodevices.
authors.affiliation: Department of Physics, The City College of New York, New York, NY 10031, United States.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Mutter
authors.affiliation: Department of Physics, The City College of New York, New York, NY 10031, United States.
authors.forename: Jessica A
authors.initials: JA
authors.lastname: Norman
authors.affiliation: Department of Chemistry, The University of Western Ontario, Ontario, Canada.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Tiedemann
authors.affiliation: Department of Physics, The City College of New York, New York, NY 10031, United States.
authors.forename: Sunaina
authors.initials: S
authors.lastname: Singh
authors.affiliation: Department of Physics, The City College of New York, New York, NY 10031, United States.
authors.forename: Sha
authors.initials: S
authors.lastname: Sha
authors.affiliation: Department of Physics, The City College of New York, New York, NY 10031, United States.
authors.forename: Sara
authors.initials: S
authors.lastname: Morsi
authors.affiliation: Department of Biochemistry, The City College of New York, New York, NY 10031, United States.
authors.forename: Ismail
authors.initials: I
authors.lastname: Ahmed
authors.affiliation: Department of Physics, The City College of New York, New York, NY 10031, United States.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Stillman
authors.affiliation: Department of Physics, The City College of New York, New York, NY 10031, United States. Electronic address: koder@sci.ccny.cuny.edu.
authors.forename: Ronald L
authors.initials: RL
authors.lastname: Koder
mesh_terms: D019943:Amino Acid Substitution; D001665:Binding Sites; D006418:Heme / Q000737:chemistry; D006420:Hemeproteins / Q000737:chemistry* / Q000235:genetics; D007211:Indoles / Q000737:chemistry*; D054833:Isoindoles; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009942:Organometallic Compounds / Q000737:chemistry*; D011485:Protein Binding; D055550:Protein Stability; D017433:Protein Structure, Secondary; D017967:Zinc Compounds
chemical_list: D006420:Hemeproteins; D007211:Indoles; D054833:Isoindoles; D009942:Organometallic Compounds; D017967:Zinc Compounds; C052159:Zn(II)-phthalocyanine; D006418:Heme
keywords: Magnetic circular dichroism; Protein design; Zinc(II) phthalocyanine; Zinc(II) phthalocyanine monosulfonate