Proton NMR study of the interaction of tin(IV) protoporphyrin IX monomers and dimers with apomyoglobin

Journal Article · Mon Jan 20 23:00:00 EST 1992 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00117a024· OSTI ID:5489011

Deeb, R S; Peyton, D H ^[1]

---

1. Portland State Univ., OR (United States)

Events during the reconstitution of apomyoglobin to form the holoprotein were probed by porphyrin-metal substitution. Thus interactions between tin(IV) protoporphyrin IX (SnPP) and equine apomyoglobin (apoEqMb), and between tin(IV) protoporphyrin IX dimers ((SnPP){sub 2}) and apoEqMb, were observed by {sup 1}H NMR and optical absorbance spectroscopic techniques. The chief advantages of using SnPP are that products and intermediates can easily be related to SnPP{center dot}EqMb which has been studied and that at least one step during reconstitution is slowed considerably as compared to heme. Reactions of apoEqMb with SnPP and (SnPP){sub 2} produce different intermediates, although the final product, SnPP{center dot}EqMb, is the same for each. An intermediate observed for reaction of SnPP with apoEqMb at pH 10 is in exchange with free SnPP, with the observed rate constant k{sub off} {approximately} 1 s{sup {minus}1}. meso-Proton resonances were assigned for this intermediate by correlation to SnPP resonances via chemical exchange. The intermediate observed for reaction of (SnPP){sub 2} with apoEqMb at pH 7.5 is heterogeneous. The reaction of either SnPP or (SnPP){sub 2} with apoEqMb at neutral pH produces another species which may be the alternate porphyrin-insertion isomer arising from a 180{degree} rotation about the {alpha},{gamma}-meso axis of the porphyrin. Although optical absorbance spectroscopy of the Soret region shows evidence for each reaction, only in combination with {sup 1}H NMR are the various processes assigned.

• OSTI ID: 5489011
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 31:2; ISSN 0006-2960; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ABSORPTION SPECTROSCOPY
BARYONS
CARBOXYLIC ACIDS
ELEMENTARY PARTICLES
FERMIONS
GLOBINS
HADRONS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
MAGNETIC RESONANCE
MOLECULAR STRUCTURE
MYOGLOBIN
NUCLEAR MAGNETIC RESONANCE
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OVERHAUSER EFFECT
PIGMENTS
PORPHYRINS
PROTEINS
PROTONS
PROTOPORPHYRINS
RESONANCE
SPECTRA
SPECTROSCOPY
VISIBLE SPECTRA