quinta-feira, 21 de julho de 2016

The complexity of the initial Enzymatic and Metabolic network of the first living cells ( progenote/LUCA ) demonstrates the requirent of a intelligent , powerful Creator

Following shows the minimal metabolic network that was required in the first supposed last universal common ancestor. Consider that this extremely complex network could not emerge through evolution, since evolution depends that this very own metabolic network was fully operational, beside dna replication, on which evolution depends. 

So the only two mechanisms that remain to explain its origin is chance/luck/self organisation, or physical necessity. We know of intelligence being able to construct electric circuits all the time.




We do not know of lucky accidents with the same capacity. We can infer therefore confidently, that the metabolic network to create the first living cell was designed. 

The Enzymatic and Metabolic Capabilities of Early Life 

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0039912#pone.0039912-Srinivasan1

We reconstruct a representative metabolic network that may reflect the core metabolism of early life forms. Our results show that ten enzyme functions, four hydrolases, three transferases, one oxidoreductase, one lyase, and one ligase, are determined by metaconsensus to be present at least as late as the last universal common ancestor. Subnetworks within central metabolic processes related to sugar and starch metabolism, amino acid biosynthesis, phospholipid metabolism, and CoA biosynthesis, have high frequencies of these enzyme functions. 





quinta-feira, 28 de abril de 2016

Cytochrome bc complexes, origin, biosynthesis etc.

The Cytochrome b6-f Complex Connects Photosystem II to Photosystem I

The electrons extracted from water by photosystem II are transferred to plastoquinol, a strong electron donor similar to ubiquinol in mitochondria. This quinol, which can diffuse rapidly in the lipid bilayer of the thylakoid membrane, transfers its electrons to the cytochrome b6-f complex, whose structure is homologous to the cytochrome c reductase in mitochondria. The cytochrome b6-f complex pumps H+ into the thylakoid space using the same Q cycle that is utilized in mitochondria, thereby adding to the proton gradient across the thylakoid membrane. The cytochrome b6-f complex forms the connecting link between photosystems II and I in the chloroplast electron-transport chain. It passes its electrons one at a time to the mobile electron carrier plastocyanin (a small copper-containing protein that takes the place of the cytochrome c in mitochondria), which will transfer them to photosystem I (Figure 14–50).


Photosystem I then harnesses a second photon of light to further energize the electrons that it receives.

The structure and function of the cytochrome b6 f complex

Molecular mechanisms of photosynthesis, Robert Blankenship, page 120

The cytochrome b6 f complex is an essential player in noncyclic and cyclic electron flow. The cytochrome b6 f complex is similar in most ways to the cytochrome bc1 complex. However, there are some important differences. The structure of the cytochrome b6 f complex is shown in Fig. 7.7.


Table 7.2 gives the identity and masses of the proteins of the cytochrome b6 f complex.


 In addition to the proteins, the complex contains chlorophyll and carotenoid molecules of unknown function. Cytochrome f is a c-type cytochrome that serves a similar functional role to cytochrome c1 in the cytochrome bc1 complex. However, the two cytochromes have very different structural features. It is an elongated protein, with largely 𝛽-sheet secondary structure. The 𝛽-sheet structure is very unusual compared with other c-type cytochromes, which are largely 𝛼-helical. Cytochrome f has a single transmembrane helical segment near the Cterminal end of the protein, which anchors the globular domain to the luminal side of the thylakoid membrane. In some species, this segment is easily cleaved from the globular portion that contains the covalently attached heme group. Cytochrome f is also unusual in that the N-terminal amino group is one of the ligands to the Fe in the heme. It donates electrons toplastocyanin (or, in some organisms, the soluble cytochrome c6). The Rieske Fe–S protein in the cytochrome b6 f complex consists of two domains: an N-terminal transmembrane helical region that anchors the protein to the membrane and a soluble domain located on the luminal side of the thylakoid membrane that contains the Fe–S redox cofactor . The soluble domain is largely 𝛽-sheet in secondary structure and is further divided into two subdomains. One of the subdomains contains the Fe–S cofactor and is structurally almost identical to the corresponding part of the Rieske protein from the cytochrome bc1 complex, while the other subdomain is very different. This is thought to reflect the different reaction partners (cytochrome c1 vs. cytochrome f) of the Rieske protein in the two types of complexes. Another important difference between the cytochrome b6 f and the cytochrome bc1 complex is the cytochrome b portion of the complex. In the cytochrome bc1 complex, cytochrome b is an integral membrane protein with eight trans membrane helices, as discussed above. However, cytochrome b6 is much smaller, with only four trans membrane helices predicted. Another subunit of the cytochrome b6 f complex, called subunit IV, exhibits sequence similarity to the C-terminal half of the cytochrome b in the bc1 complex. Subunit IV contains three predicted transmembrane helices; the eighth transmembrane helix of the cytochrome bc1 complex is missing. A surprising difference between the cytochrome b6 f and bc1 complexes is the presence of an additional heme group, called heme cn in the cytochrome b6 f complex. This heme has a single thioether linkage to the protein instead of two linkages found in almost every other c-type cytochrome. This was first discovered in the cytochrome b6 f complex isolated from the green alga Chlamydomonas reinhardtii , but is also found in the complex from cyanobacteria. In addition to the subunits described above, the cytochrome b6 f complex contains some other protein subunits not found in the cytochrome bc1 complex (Table 7.2). The cytochrome b6 f complex surprisingly contains one molecule each of chlorophyll and 𝛽 carotene, although it is not known if these pigments serve an important functional role. The cytochrome b6 f complex is also dimeric in vivo, like the cytochrome bc1 complex, although it can easily become monomeric and inactive once isolated .