Copper cyclic peptide complexes

Cyclic peptides can be viewed as a step on the way from the modeling of unconstrained peptides to folded proteins. The copper(II) complex of a cyclic octapep-tide has been investigated by molecular mechanics and EPR spectroscopy and the structure was found to be in accord with those of closely related complexes 205]. Similar combined approaches are also applicable to metalloproteins. 

In all extractions of L. patella, the major compounds isolated are always cyclic peptides, with one of the patellamides usually the most abundant of these. " There has been only one reported case of L. patella which did not have Prochloron as its symbiont. When this sample was extracted no cyclic peptides were isolated. This supports the case for their being produced by Prochloron rather than the host. The production of these compounds, by either the host or symbiont, is costly to the internal metabolism of the producing organism and they must therefore play some ecological role. The selectivity and structural studies show these peptides are most suited to bind copper. Copper is therefore proposed to be the ecologically relevant metal for the patellamides. It is possible that the patellamide/copper complexes might be co-factors in enzymatic processes. We will discuss a few further possibilities here. 

Are they involved in carbon metabolism There are many candidates in the carbon metabolism of Prochloron that could be converted to the C3Hs03 moiety of the 2Cu patellamide C complex. Studies have shown that L. patella actively removes glycolate to encourage photosynthesis by prochloron Are the copper complexes of these cyclic peptides involved as enzymic cofactors in this process ... 

---