scholarly journals AplA, a Member of a New Class of Phycobiliproteins Lacking a Traditional Role in Photosynthetic Light Harvesting

2004 ◽  
Vol 186 (21) ◽  
pp. 7420-7428 ◽  
Author(s):  
Beronda L. Montgomery ◽  
Elena Silva Casey ◽  
Arthur R. Grossman ◽  
David M. Kehoe
Keyword(s):  
Amino Acid ◽  
Tertiary Structure ◽  
Light Harvesting ◽  
Water Soluble ◽  
Amino Acid Residues ◽  
Subunit Interactions ◽  
Traditional Role ◽  
Light Harvesting Complexes ◽  
Fremyella Diplosiphon ◽  
New Class

ABSTRACT All known phycobiliproteins have light-harvesting roles during photosynthesis and are found in water-soluble phycobilisomes, the light-harvesting complexes of cyanobacteria, cyanelles, and red algae. Phycobiliproteins are chromophore-bearing proteins that exist as heterodimers of α and β subunits, possess a number of highly conserved amino acid residues important for dimerization and chromophore binding, and are invariably 160 to 180 amino acids long. A new and unusual group of proteins that is most closely related to the allophycocyanin members of the phycobiliprotein superfamily has been identified. Each of these proteins, which have been named allophycocyanin-like (Apl) proteins, apparently contains a 28-amino-acid extension at its amino terminus relative to allophycocyanins. Apl family members possess the residues critical for chromophore interactions, but substitutions are present at positions implicated in maintaining the proper α-β subunit interactions and tertiary structure of phycobiliproteins, suggesting that Apl proteins are able to bind chromophores but fail to adopt typical allophycocyanin conformations. AplA isolated from the cyanobacterium Fremyella diplosiphon contained a covalently attached chromophore and, although present in the cell under a number of conditions, was not detected in phycobilisomes. Thus, Apl proteins are a new class of photoreceptors with a different cellular location and structure than any previously described members of the phycobiliprotein superfamily.

Evolutionary divergence and salinity-mediated selection in halophilic archaea

1997 ◽  
Vol 61 (1) ◽  
pp. 90-104
Author(s):  
P P Dennis ◽  
L C Shimmin
Keyword(s):  
Amino Acid ◽  
Tertiary Structure ◽  
Halophilic Archaea ◽  
Amino Acid Replacement ◽  
Evolutionary Divergence ◽  
Ionic Balance ◽  
Amino Acid Residues ◽  
Nucleotide Substitutions ◽  
Nonsynonymous Substitutions ◽  
Environmental Salinity

Halophilic (literally salt-loving) archaea are a highly evolved group of organisms that are uniquely able to survive in and exploit hypersaline environments. In this review, we examine the potential interplay between fluctuations in environmental salinity and the primary sequence and tertiary structure of halophilic proteins. The proteins of halophilic archaea are highly adapted and magnificently engineered to function in an intracellular milieu that is in ionic balance with an external environment containing between 2 and 5 M inorganic salt. To understand the nature of halophilic adaptation and to visualize this interplay, the sequences of genes encoding the L11, L1, L10, and L12 proteins of the large ribosome subunit and Mn/Fe superoxide dismutase proteins from three genera of halophilic archaea have been aligned and analyzed for the presence of synonymous and nonsynonymous nucleotide substitutions. Compared to homologous eubacterial genes, these halophilic genes exhibit an inordinately high proportion of nonsynonymous nucleotide substitutions that result in amino acid replacement in the encoded proteins. More than one-third of the replacements involve acidic amino acid residues. We suggest that fluctuations in environmental salinity provide the driving force for fixation of the excessive number of nonsynonymous substitutions. Tinkering with the number, location, and arrangement of acidic and other amino acid residues influences the fitness (i.e., hydrophobicity, surface hydration, and structural stability) of the halophilic protein. Tinkering is also evident at halophilic protein positions monomorphic or polymorphic for serine; more than one-third of these positions use both the TCN and the AGY serine codons, indicating that there have been multiple nonsynonymous substitutions at these positions. Our model suggests that fluctuating environmental salinity prevents optimization of fitness for many halophilic proteins and helps to explain the unusual evolutionary divergence of their encoding genes.

Isolation and characterization of three membranebound chlorophyll-protein complexes from four dinoflagellate species

1993 ◽  
Vol 340 (1294) ◽  
pp. 381-392 ◽  
Keyword(s):  
Energy Transfer ◽  
Photosystem I ◽  
Light Harvesting ◽  
Protein Complexes ◽  
Gradient Centrifugation ◽  
Water Soluble ◽  
Molar Ratio ◽  
Light Harvesting Complexes ◽  
Light Harvesting Complex ◽  
Isolation And Characterization

Employing discontinuous sucrose density gradient centrifugation of n -dodecyl β-d-maltoside-solubilized thylakoid membranes, three chlorophyll (Chl)-protein complexes containing Chl a , Chl c 2 and peridinin in different proportions, were isolated from the dinoflagellates Symbiodinium microadriaticum, S. kawagutii, S. pilosum and Heterocapsa pygmaea . In S. microadriaticum , the first complex, containing 13% of the total cellular Chl a , and minor quantities of Chl c 2 and peridinin, is associated with polypeptides with apparent molecular mass ( M r ) of 8-9 kDa, and demonstrated inefficient energy transfer from the accessory pigments to Chl a . The second complex contains Chl a , Chl c 2 and peridinin in a molar ratio of 1:1:2, associated with two apoproteins of M r 19-20 kDa, and comprises 45%, 75% and 70%, respectively, of the cellular Chl a , Chl c 2 and peridinin. The efficient energy transfer from Chl c 2 and peridinin to Chl a in this complex is supportive of a light-harvesting function. This Chl a - c 2 - peridin-protein complex represents the major light-harvesting complex in dinoflagellates. The third complex obtained contains 12% of the cellular Chl a , and appears to be the core of photosystem I, associated with a light-harvesting complex. This complex is spectroscopically similar to analogous preparations from different taxonomic groups, but demonstrates a unique apoprotein composition. Antibodies against the water-soluble peridinin-Chl a -protein (sPCP) light-harvesting complexes failed to cross-react with any of the thylakoid-associated complexes, as did antibodies against Chl a - c -fucoxanthin apoprotein (from diatoms). Antibodies against the P 700 apoprotein of plants did not cross-react with the photosystem I complex. Similar results were observed in the other dinoflagellates.

scholarly journals Identification of Amino Acid Residues in CD81 Critical for Interaction with Hepatitis C Virus Envelope Glycoprotein E2

2000 ◽  
Vol 74 (8) ◽  
pp. 3642-3649 ◽  
Author(s):  
Adrian Higginbottom ◽  
Elizabeth R. Quinn ◽  
Chiung-Chi Kuo ◽  
Mike Flint ◽  
Louise H. Wilson ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Amino Acid ◽  
Envelope Glycoprotein ◽  
Tertiary Structure ◽  
Antibody Binding ◽  
Viral Envelope ◽  
Amino Acid Residues ◽  
Virus Envelope ◽  
Glycoprotein E2

ABSTRACT Human CD81 has been previously identified as the putative receptor for the hepatitis C virus envelope glycoprotein E2. The large extracellular loop (LEL) of human CD81 differs in four amino acid residues from that of the African green monkey (AGM), which does not bind E2. We mutated each of the four positions in human CD81 to the corresponding AGM residues and expressed them as soluble fusion LEL proteins in bacteria or as complete membrane proteins in mammalian cells. We found human amino acid 186 to be critical for the interaction with the viral envelope glycoprotein. This residue was also important for binding of certain anti-CD81 monoclonal antibodies. Mutating residues 188 and 196 did not affect E2 or antibody binding. Interestingly, mutation of residue 163 increased both E2 and antibody binding, suggesting that this amino acid contributes to the tertiary structure of CD81 and its ligand-binding ability. These observations have implications for the design of soluble high-affinity molecules that could target the CD81-E2 interaction site(s).

A Rubber-Like Protein in Insect Cuticle

1960 ◽  
Vol 37 (4) ◽  
pp. 889-907 ◽  
Author(s):  
TORKEL WEIS-FOGH
Keyword(s):  
Amino Acid ◽  
Tertiary Structure ◽  
Three Dimensional ◽  
Water Soluble ◽  
Insect Cuticle ◽  
Peptide Backbone ◽  
Experimental Proof ◽  
Dimensional Network ◽  
New Type ◽  
Elastic Protein

1. A new type of hyaline, colourless cuticle, called rubber-like cuticle, is described and analysed qualitatively with respect to mechanical behaviour, structure and composition. Externally it is covered by ordinary thin epicuticle, but otherwise it represents the simplest type of cuticle known and consists only of thin continuous lamellae of chitin (0-2 µ) separated and glued together by an elastic protein, resilin, not hitherto described. There are only traces of water-soluble substances present and resilin sometimes occurs as pure, hyaline patches more than 100 µ thick and suitable for macroscopic experiments. 2. In all physical respects, resilin behaves like a swollen isotropic rubber but the rigid experimental proof is given elsewhere (Weis-Fogh, 1961). An outstanding feature is the complete lack of flow not paralleled by other natural or synthetic rubbers. 3. Resilin resembles elastin but it is devoid of colour and has a different and characteristic amino-acid composition (Bailey & Weis-Fogh, 1961). The nature of the cross-linkages is unknown at present but they are extremely stable, of a co-valent type and different from other known cross-linkages in proteins. This accounts for its insolubility and resistance to all agents which do not break the peptide backbone. 4. Resilin is a structure protein in which the primary chains show little or no tendency to form secondary structures; they are bound together in a uniform three-dimensional network (the tertiary structure) with no potential limits as to size.

Specific water-soluble substrates for chymotrypsin: Attempts for compensating diminished P1-S1 interactions

1988 ◽  
Vol 53 (11) ◽  
pp. 2884-2889 ◽  
Author(s):  
Volker Schellenberger ◽  
Ute Schellenberger ◽  
Hans-Dieter Jakubke
Keyword(s):  
Amino Acid ◽  
Methyl Esters ◽  
Water Soluble ◽  
Amino Acid Residues ◽  
Substrate Properties ◽  
Ester Moiety ◽  
Benzyl Esters ◽  
Peptide Esters ◽  
Acyl Donors ◽  
Positively Charged

N-Maleyl-L-amino acid and peptide esters were synthesized and employed as substrates for α-chymotrypsin. From the kcat/KM values can be suggested that benzyl esters are significantly better substrates than the appropriate methyl esters. Further improvement in the substrate properties results from the introduction of the p-nitrobenzyl ester moiety. The choline ester of benzyloxycarbonyl-L-phenylalanine with the highest kcat/KM value confirmed the P1' leaving group specificity for positively charged residues. From the kinetic data can be concluded that acyl donors with high kcat/KM values, which are useful in kinetically controlled enzymatic peptide synthesis, need not contain aromatic amino acid residues in the P1 position.

scholarly journals Purification, Characterization, and Molecular Analysis of the Gene Encoding Glucosyltransferase fromStreptococcus oralis

2000 ◽  
Vol 68 (5) ◽  
pp. 2475-2483 ◽  
Author(s):  
Taku Fujiwara ◽  
Tomonori Hoshino ◽  
Takashi Ooshima ◽  
Shizuo Sobue ◽  
Shigeyuki Hamada
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
Pcr Primers ◽  
Water Soluble ◽  
Oral Streptococci ◽  
Amino Acid Residues ◽  
Gene Encoding ◽  
Streptococcus Sanguis ◽  
Specific Nucleotide Sequence ◽  
Species Specific

ABSTRACT Streptococcus oralis is a member of the oral streptococcal family and an early-colonizing microorganism in the oral cavity of humans. S. oralis is known to produce glucosyltransferase (GTase), which synthesizes glucans from sucrose. The enzyme was purified chromatographically from a culture supernatant of S. oralis ATCC 10557. The purified enzyme, GTase-R, had a molecular mass of 173 kDa and a pI of 6.3. This enzyme mainly synthesized water-soluble glucans with no primer dependency. The addition of GTase markedly enhanced the sucrose-dependent resting cell adhesion of Streptococcus mutans at a level similar to that found in growing cells of S. mutans. The antibody against GTase-R inhibited the glucan-synthesizing activities ofStreptococcus gordonii and Streptococcus sanguis, as well as S. oralis. The N-terminal amino acid sequence of GTase-R exhibited no similarities to known GTase sequences of oral streptococci. Using degenerate PCR primers, an 8.1-kb DNA fragment, carrying the gene (gtfR) coding for GTase-R and its regulator gene (rgg), was cloned and sequenced. Comparison of the deduced amino acid sequence revealed that thergg genes of S. oralis and S. gordonii exhibited a close similarity. The gtfR gene was found to possess a species-specific nucleotide sequence corresponding to the N-terminal 130 amino acid residues. Insertion oferm or aphA into the rgg orgtfR gene resulted in decreased GTase activity by the organism and changed the colony morphology of these transformants. These results indicate that S. oralis GTase may play an important role in the subsequent colonizing of mutans streptoccoci.

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