The three-dimensional structure of bovine pancreatic (bp) DNase revealed that its N- and C-termini form an antiparallel β-sheet structure. The involvement of this β-sheet structure in the active protein folding of bpDNase was thus investigated via a series of deletion and substitution variants. Several substitution variants of N-terminal Leu1 and C-terminal Leu259, and one variant with only the last Thr260 deleted, remained fully active. However, the other deletion variants, in which 2−10 amino acid residues were removed from the C- or N-terminus, all lost the DNase activity. The results indicated that the backbone hydrogen bonding in the antiparallel β-sheet, rather than the side-chain interactions, is crucial for the correct protein folding. When the deletion variants were complemented with synthetic peptides of the deleted N- or C-terminal sequences, the DNase activity was generated. The highest DNase activity was generated when the C-terminal 10-residue-deleted brDNase(Δ251−260) was admixed with the C-terminal 10-residue peptide (peptide C10) in a molar ratio of 1:400. The noncovalent binding between brDNase(Δ251−260) and peptide C10 exhibited a dissociation constant of 48 μM. Circular dichroism spectra showed that the deletion variants were partially folded with mainly helical structures and that admixture with corresponding peptides facilitated their folding into the nativelike β-sheet-rich structure. Thermal denaturation profiles also revealed that the transition temperature for brDNase(Δ251−260) was increased from 55 to 63 °C after incubation with peptide C10. The folding activation process for the deletion variant occurred in two stages, and Ca2+ was required.
I briefly summarize the discussion in the Zeitschrift für Kristallographie on "What is a crystal?" [1].The best upto-date answer is that it is a solid whose Fourier spectrum contains a pure point part, in other words, it shows Bragg peaks.That rises the more general question about "What diffracts and how?" Hence, there is growing interest in quasiregular heterostructures [2].These are layer structures artificially fabricated according to certain algorithms, mainly substitution sequences.Some outstanding examples are Fibonacci, Thue-Morse, Rudin-Shapiro, paperfolding and period doubling chains (finite parts of sequences) [3].Their spectral properties are of great interest.
CRISPR-Cas systems are adaptive immune mechanisms present in most prokaryotes that play an important role in the adaptation of bacteria and archaea to new environments. Shewanella algae is a marine zoonotic pathogen with worldwide distribution, which accounts for the majority of clinical cases of Shewanella infections. However, the characterization of Shewanella algae CRISPR-Cas systems has not been well investigated yet. Through whole genome sequence analysis, we characterized the CRISPR-Cas systems in S. algae. Our results indicate that CRISPR-Cas systems are prevalent in S. algae, with the majority of strains containing the Type I-F system. This study provides new insights into the diversity and function of CRISPR-Cas systems in S. algae and highlights their potential role in the adaptation and survival of these marine pathogens.
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