Heme peptide

The use of disulfide linked di-a-helical peptides for the self-assembly of a heme-peptide model compounds has also been explored by Benson et al. (109). Conceptually analogous to the larger heme-protein systems utilized by Dutton and co-workers, to be detailed later, the incorporation of C4 S5mimetric Co(III)-porphyrins, based on coproporphyrin and octaethylporphyrin, resulted in helical induction comparable to that observed in the covalent PSM systems. 

These minimalistic peptide scaffolds potentially provide a biologically relevant laboratory in which to explore the details of heme-peptide interactions and, with development, perhaps approach the observed range of natural heme protein fimction. These heme-peptide systems are more complex than typical small molecule bioinorganic porphyrin model compoimds, and yet are seemingly not as enigmatic as even the smallest natural heme proteins. Thus, in the continuum of heme protein model complexes these heme-peptide systems lie closer to, but certainly not at, the small molecule limit which allows for the effects of single amino acid changes to be directly elucidated. 

In the smaller peptide systems, only three reports containing heme peptide reduction potentials have been published however, this limited data set reveals two important aspects of cytochrome design. Figure 12 shows that Huffman et al. (125) have convincingly illustrated a direct... 

Figure 83. Model of haemoglobin. Explanation H - heme. Peptides are part of myoglobin.

The NMR of ferrous complexes of MPll and MP8 in aqueous SDS solutions has been studied the spectra are very broad and ill-resolved [23]. The heme proton resonances appear in the range 15 to 30 ppm and resemble those of ferrous hemoproteins. The similarity in the linewidths and spectral range of the heme protons in these ferrous peptide complexes with the ferrous hemoproteins suggests that the larger size of the heme peptide restricts the mobility of the molecule inside the micelles compared to that in case of the protoporphyrin complex in micellar solutions, where the spectrum is better resolved. 

Harbury HA, Cronin JR, Fanger MW et al (1965) Complex formation between methionine and a heme peptide from cytochrome c. Proc Natl Acad Sci USA 54 1658-1664... 

The problems connected with the high cost and low stability of peroxidases, which limits their potential applications in processes of industrial interest, can be possibly overcome, at least in part, by the use of heme-peptide complexes as small-size peroxidase analogs. In this context, we will consider only the heme-peptide complexes more strictly related to the peroxidases, and will not deal with the extensive literature about catalytic oxidations by synthetic metalloporphyrins. It is difficult to reproduce in a synthetic molecule the peculiar features of complex enzymes such as... 

Nicolis S, Casella L, Roncone R, Dallacosta C, Monzani E (2007) Heme-peptide complexes as peroxidase models. C R Chimie 10 380-391... 

Casella L, De Gioia L, Frontoso Silvestri G (2000) Covalently modified microperoxidases as heme-peptide models for peroxidases. J Inorg Biochem 79 31 -0... 

The most valuable confirmation of this view to date is, without doubt, to be found in the known structures of homologous proteins and peptide hormones, that is compounds of identical biological function isolated from different species. As is well known, the primary structures of the homologous insulins, corticotropins, hypertensins, posterior pituitary hormones, and heme peptide sequences from cytochromes c are closely similar and differ only at certain definite sites in the peptide chains. These can, in particular, serve as a useful point of departure in a search for more general principles governing protein structure, and in the comparison of different proteins. 

A particularly fine example of multiple recurrences of short as well as longer sequences, with standard interchanges and short-range rearrangements, is provided by the heme peptide isolated as a fragment from the heme protein of the photoanaerobe Chromatium (strain D) (Dus et al., 1961)... 

Fig. 8. Internal regularities in the structure of the heme peptide from Chromalium...

Cytochrome c Pepsin, trypsin Heme peptides Tuppy (1958)... 

Chromatium heme protein Pepsin Heme peptide Dus et al. (1962)... 

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