Bacterial type, amino acid sequences

Studies on the bacterial type 1 protein azurin have been extensive. Ten different azurin amino-acid sequences have been determined with 47 out of 129 residues (Mf 14,(XX)) conserved. Reduction potentials are in the range 280 339 mV at... 

Whereas the electron acceptors in the anaerobic organisms are the bacterial-type ferredoxins that contain [4Fe-S] clusters as the redox center, in the case of the halobacteria the electrons are transferred to [2Fe-S] ferredoxins. These ferredoxins were isolated from two different halobacteria and their amino acid sequences were determined (Hase et al., 1977, 1980) and shown to be highly homologous to the chloroplast (and cyanobacterial) ferredoxins. The implications of these perplexing findings for the question of the molecular evolution of the system is discussed in detail in Kerscher and Oesterhelt (1982). 

Amino acid sequence comparison of the different Ty s shows that they are structurally related. The sequence identity is 24% between bacterial and fungal Ty and 26% between mouse and N. crassa Ty. A comparison of all three types of Ty (bacterial, ftmgal, and mammalian) reveals a sequence identity of only 8.7%. 

Zinc efflux is mediated by a zinc exporter known as ZntA (Zn + transport or tolerance), a membrane protein which was identified through studies of bacterial strains that were hypersensitive to zinc and cadmium. Sequence inspection revealed that ZntA was a member of the family of cation transport P-type ATPases, a major family of ion-translocating membrane proteins in which ATPase activity in one portion of the protein is used to phophorylate an aspartate within a highly conserved amino acid sequence, DKTG, in another portion of the protein. The cysteine rich N-terminus of these soft metal transport proteins contains several metal-binding sites. How the chemical energy released by ATP hydrolysis results in metal ion transport is not yet known, in part because there is only partial information about the structures of these proteins. The bacterial zinc exporter also pumps cadmium and lead and is therefore also involved in protection from heavy metal toxicity (see Metal Ion Toxicity). 

The outgroup was the consensus sequence of four bacterial type 111 PKSs. The bacterial enzymes extend the array of the polyketide scaffolds. They share only -25% amino acid sequence identity with plant PKSs and each other 43). The phylogenetic tree reflected the systematic grouping of the higher plants. The PKSs from angiosperms fall into two clusters. One cluster comprises CHSs including the enzymes from H. androsaemum and S. aucuparia cell cultures. 

Eukaryotic PNPTs are localized in the membrane of the endoplasmic reticulum (ER) where they catalyze the first step in N-linked glycoprotein biosynthesis resulting in a Dol-PP-GlcNAc intermediate. In contrast, bacterial PNPTs such as WecA, MraY, WbpL, and WbcO utilize different N-acetylhexosamine substrates and they also differ in their susceptibility to selective inhibitors. Several regions of conserved amino acid sequence can be found in bacterial and eukaryotic members of the PNPT family. It is plausible that all the members of this family utilize a common enzymatic mechanism for the formation of the phosphodiester bond. However, bacterial and eukaryotic PNPTs differ in their substrate specificity for various N-acetylhexosamine substrates and also they can discriminate the type of polyisoprenol phosphate. Und-P contains 11 isoprene units all of which are fully unsaturated, while Dol-P can be made of 15-19 isoprene units that have a saturated ct-isoprene. The ct-isoprene is the phosphorylated end of the molecule, which participates in the phosphodiester bond formation with the N-acetylhexosamine-l-P. Therefore, the ability of eukaryotic and bacterial enzymes to exquisitely discriminate their lipid substrate is likely a reflection of evolutionary divergence. 

A detailed discussion of the state of knowledge of amino acid sequences of bacterial c-type cytochromes has been rendered superfluous by an excellent recent review by Ambler (362), from whose laboratory many of these sequences have come. The sequences in that review, identified for reference in Table XXIII, are all that are presently known besides the C2 and C550 sequences of Table VII. With the availability of primary... 

The FcjS -type ferredoxins can be arranged into three distantly related classes based on amino acid sequence homologies bacterial-, plant-, and vertebrate-type . Extensive information on the function and mechanisms of this system has been gained through work on the bacterial P450cam system in Pseudomonas putida, which catalyzes the conversion of rf-camphor to 5-exo-hydroxy-camphor. In P putida, the iron-sulfur protein is putidaredoxin (Pdx), a 106 amino acid residue ferredoxin. For catalysis, two reducing equivalents are sequentially transferred from NADH... 

Arsenate reductases, initially characterized from plasmid R773 of gramnegative bacteria and plasmid pI258 of gram-positive S. aureus both reduce arsenate to arsenite and both confer arsenate resistance (21,34,36). However, their in vitro measured properties are very different and their energy coupling is different. As the amino acid sequences are only 15% identical, it appears that arsenate reductase enzymatic activity evolved twice independently among bacterial types... 

The ability of various diaminopyrimidines to distinguish between analogous forms of the enzyme dihydrofolate reductase is the basis of some of the best contemporary anti-malarial and anti-bacterial therapy (see Section 4.0, p. 123, Tables 4.1 and 4.2, and Section 9.3.3 and 9.6). Let us first look at the differences that exist between various vertebrate types of the enzyme, none of which is much inhibited by trimethoprim (4.P), and then proceed to invertebrate types, which are highly susceptible to this drug. The enzyme from chicken liver has only 75% identity of amino acid sequence with that from ox liver. Moreover, methylmercuric hydroxide activates the avian type twelvefold whereas it inactivates the bovine type. The avian type is much richer in basic amino acids and has an isoelectric point of 8.4 compared to 6.8 for the bovine type. This result is achieved in the avian type by the presence of lysine at positions 32,106, and 154, whereas the bovine type has glycine, threonine, and glutamic acid, respectively, in these positions (Kumars/a/., 1980). 

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