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Research has been conducted on the cytochrome c-549 and cytochrome c (sub)6. The X-ray structures of these proteins isolated from cyanobacterium Arthrospira maxima have been investigated and the results indicate that their structures are similar.

Biochemical characterization, crystallization and structure determination studies were undertaken to determine the crystal structure of the high-potential iron-sulfur protein from Chromatium purpuratum. The crystal structure was determined with a resolution of 2.7 angstrom units. The protein appears to undergo dimerization via nonspecific interactions at a conserved hydrophobic domain.

Electron transfer proteins are isolated and characterized from the marine purple-sulfur bacterium Chromatium purpuratum. Redox titrations of the flavocytochrome c hemes indicate two components with midpoint potential values of +15 and -120 mV, which is similar to that of the flavocytochrome isolated from the thermophilic Chromatium tepidum. There is also substantial homology to the main structure of the flavocytochrome c of Chromatium vinosum. In contrast, the C. purpuratum high-potential iron-sulfur protein differs from those isolated from other photosynthetic bacteria.

The purple-sulfur bacterium Chromatium purpuratum, which has an unusual peripheral antenna, has certain photosynthetic apparatus phenotypic features that are related to the green-sulfur bacteria and other purple bacteria. The peripheral antenna is associated with a carotenoid and three proteins.

The characterization of the excited state dynamics of 3'-hydroxyechinenone (hECN) both in solution and bound to the orange carotenoid binding protein (OCP) in order to disclose the effects of hECN -protein interaction on excited states properties of the hECN is reported. The binding-induced conformational change and activation of the intramolecular charge-transfer state that leads to a shortening of hECN lifetime effectively makes the protein-bound hECN a more effective energy dissipator.

Recently a new family of carotenoproteins, homologues of the N-terminal domain of the orange carotenoid protein (NTD-OCP), have been identified in cyanobacteria. These homologues are called helical carotenoid proteins (HCPs) as they are all predicted to maintain the all-helical structure of the NTD-OCP and to bind carotenoids. Here, HCP2 and HCP3 isolated from the cyanobacterium Tolypothrix PCC 7601 were studied by ultrafast transient absorption spectroscopy to explore the excited-state dynamics of the bound carotenoid, canthaxanthin. The lowest excited state, S 1 , of canthaxanthin in both HCPs yields a lifetime of 3.5 ps; it is thus shorter than for canthaxanthin in solution (4.5 ps). This is because of the longer effective conjugation of canthaxanthin in HCPs, as one of the terminal rings is in an s-trans configuration. Use of two different excitation wavelengths, 470 and 570 nm, revealed excitation wavelength dependent spectroscopic response. Additional excited-state absorption bands are observed after excitation at 470 nm for both HCPs, proving the presence of more than one ground state conformer.

The orange carotenoid protein (OCP) plays an important role in photoprotection in cyanobacteria, which is achieved by the photoconversion from the orange dark state (OCP O ) to the red active state (OCP R ). Using Raman optical activity (ROA), we studied the conformations of the carotenoid chromophore in the active sites of OCP O and OCP R . This ROA measurement directly observed the chromophore conformation of native OCP in solution, and the measurement of OCP R first demonstrated the ROA spectroscopy for the transient species. For OCP O , the spectral features of ROA were mostly reproduced by the quantum chemical calculation based on the crystal structure of the OCP. Within the spatial resolution (∼2 Å), a slight modification of the polyene-chain distortion improved the agreement between the observed and calculated ROA spectra. While the crystal structure of OCP R is not available, the ROA spectrum of OCP R was reproduced by using the crystal structure of red carotenoid protein (RCP), an OCP R proxy. The present results showed that the chromophore conformations in the crystal structures of OCP and RCP hold true for OCP O and OCP R in solution. Particularly, ROA spectroscopy of the native OCP R provides a direct support for the 12 Å translocation of chromophore in the photoactivation, which was proposed by X-ray crystallography using RCP [R. L. Leverenz, M. Sutter, et al. Science 2015, 348, 1463-1466].

Bacterial microcompartments (BMCs) are self-assembling organelles composed entirely of protein. Depending on the enzymes they encapsulate, BMCs function in either inorganic carbon fixation (carboxysomes) or organic carbon utilization (metabolosomes). The hallmark feature of all BMCs is a selectively permeable shell formed by multiple paralogous proteins, each proposed to confer specific flux characteristics. Gene clusters encoding diverse BMCs are distributed broadly across bacterial phyla, providing a rich variety of building blocks with a predicted range of permeability properties. In theory, shell permeability can be engineered by modifying residues flanking the pores (symmetry axes) of hexameric shell proteins or by combining shell proteins from different types of BMCs into chimeric shells. We undertook both approaches to altering shell properties using the carboxysome as a model system. There are two types of carboxysomes, α and β. In both, the predominant shell protein(s) contain a single copy of the BMC domain (pfam00936), but they are significantly different in primary structure. Indeed, phylogenetic analysis shows that the two types of carboxysome shell proteins are more similar to their counterparts in metabolosomes than to each other. We solved high resolution crystal structures of the major shell proteins, CsoS1 and CcmK2, and the presumed minor shell protein CcmK4, representing both types of cyanobacterial carboxysomes and then tested the interchangeability. The in vivo study presented here confirms that both engineering pores to mimic those of other shell proteins and the construction of chimeric shells is feasible.