Study On The Senior Structure Of PMetMbase A By Spectra

pMetMbase A was one of the key enzymes that was found in the myoglobin redox system (MGRS). Its senior structure and domains need to be further recognized. We purified93%electrophoretically pure pMetMbase A from fresh myocardium in pork. Its ultramicro and spectroscopic structural characteristics have been identified by scanning electron microscopy (SEM), X-ray diffraction (XRD), circular dichroism (CD) and fluorescence spectra (FS). This study also explored the effect of ultraviolet (UV) on electronic transfer and redox function of pMetMbase.1Freezing-dry powder of pMetMbase A was90.5%±8.56%of crystalline with cluster-like protrusions. Compared to standard compounds in XRD database, it was suggested that pMetMbase A contain special functional group as iron porphyrin ring (heme-Fe), which contain perylene benzo, pyridine, imidazole and methyl amine. These compounds could be composed of heme via alkylating. Its anhydrous crystalline tended to hexagonal.2In nature statue, the secondary structure of pMetMbase A was of88.1%a-helix,0.8%p-strand,4.1%β-turn and7.1%random under2.16×10-2mmol/L in190-250nm of CD, so it was belonged to a full a-type protein. Aromatic amino acids (P-AAs) and S-S groups had CD spectra at250-310nm near-ultraviolet region. Compared with43proteins in SP43database, the molecular information of pMetMbase A was very different to them (p=0.02). And then there was a significant CD phase difference between Hb/Mb and pMetMbase A with itself special secondary structure.3Domains of P-AAs and heme-Fe were at311nm (Tyr-),349.5nm (Trp-) and650nm, respectively, by fluorescence spectra. It was found that their fluorescence lifetime were3.00ns/P-AAs and2.41ns/heme-Fe. The later was shorter than the former. It was result that heme-Fe was a core chemical group for electron transfer and redox in MGRS.4The tertiary and secondary structure of pMetMbase A could be damaged with obviously fluorescent shift (p<0.01) under the UV exposure. Because of this reason, domain of P-AAs moved to red shift of10nm, while domain of heme-Fe moved to blue shift of21.7nm and their fluorescent spectra were getting weakly. The heme-Fe at core area was exposed when the backbone of peptide chain was destructed and the tertiary structure of the enzyme was depolymerized. After exposed60min under UV, a-helix was unfolded and replaced by β-turns and unordered continueously. At the same time, five-coordinate high spin in heme-Fe turned to six-coordinated low spin so that pMetMbase A was lost its redox in MGRS ultimately.