title: Myoglobin with chlorophyllous chromophores: influence on protein stability.
abstract: The stabilities of myoglobin, apo-myoglobin, and of two myoglobins with chlorophyllous chromophores (Zn-pheophorbide a and Zn-bacteriopheophorbide a), have been studied by thermal and chemical denaturation. With guanidinium chloride, the stability order is myoglobin>Zn-pheophorbide-myoglobin>Zn-bacteriopheophorbide-myoglobin approximately apo-myoglobin. The thermal behavior is more complex. The transition temperature of thermal unfolding of the apoprotein (62.4 degrees C) is increased by Zn-pheophorbide a (83.9 degrees C) and Zn-bacteriopheophorbide a (82.6 degrees C) to a similar degree as by the native chromophore, heme (83.5 degrees C). The recovery with Zn-pheophorbide (92-98%) is even higher than with heme (74-76%), while with Zn-bacteriopheophorbide (40%) it is as low as with the apoprotein (42%). Recovery also depends on the rates of heating, and in particular the time spent at high temperatures. It is concluded that irreversibility of unfolding is related to loss of the chromophores, which are required for proper re-folding.
authors.affiliation: Department of Biologie I, Botanik, Menzinger Str. 67, D-80638 München, Germany.
authors.forename: Dejan
authors.initials: D
authors.lastname: Marković
authors.forename: Stefanie
authors.initials: S
authors.lastname: Pröll
authors.forename: Claudia
authors.initials: C
authors.lastname: Bubenzer
authors.forename: Hugo
authors.initials: H
authors.lastname: Scheer
mesh_terms: D000042:Absorption; D000818:Animals; D001429:Bacteriochlorophylls / Q000737:chemistry*; D002734:Chlorophyll / Q000031:analogs & derivatives* / Q000737:chemistry; D002942:Circular Dichroism; D019791:Guanidine / Q000737:chemistry; D009211:Myoglobin / Q000737:chemistry*; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D044366:Transition Temperature; D014466:Ultraviolet Rays
chemical_list: D001429:Bacteriochlorophylls; D009211:Myoglobin; D002734:Chlorophyll; C032623:pheophorbide a; D019791:Guanidine