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A putative type II pullulanase gene, pulP , was identified in Bifidobacterium adolescentis P2P3. PulP possesses an α-amylase domain at the N-terminus and a pullulanase type I domain at the C-terminus, as well as three carbohydrate-binding modules (one CBM25 and two CBM41s) between them. The native PulP and four truncated mutant recombinant proteins (PulPΔCΔP, PulPΔP, PulPΔAΔC, and PulPΔA), in which each of the two catalytic domains and/or the CBMs were deleted, were produced in Escherichia coli and their specific properties were characterized. The removal of either catalytic domain abolished the corresponding catalytic activity of the wild-type enzyme. Deletion of the C-terminal domain resulted in a drastic decrease in the optimal temperature and thermostability, indicating that the pullulanase domain might be related to the temperature dependency of the enzyme. In addition, the elimination of the CBMs in the mutant proteins led to a loss of binding affinity toward raw substrates as well as the loss of their hydrolysis activities compared to the wild-type enzyme. HPAEC and TLC analyses proved that PulP and its mutants could hydrolyze α-glucans into maltotriose as their main product. These results suggest that PulP may play an important role in α-glucan metabolism in B. adolescentis P2P3. • PulP is a type II pullulanase identified in Bifidobacterium adolescentis P2P3. • PulP and its mutants could hydrolyze α-glucans into maltotriose as their main product. • The deletion of C-terminal resulted in a drastic decrease in the optimal temperature and thermostability. • The elimination of the CBM led to a loss of binding affinity toward raw substrates. [ABSTRACT FROM AUTHOR]

• A new alkaline pullulanase gene (pulSL3) was cloned and hetero-expressed. • rPulSL3 is highly active and stable at the concentration of NaCl up to 4 M. • rPulSL3 has very strong resistance to sodium dodecyl sulfate (SDS). • N-terminal truncated protein exhibited excellent enzyme properties. A new pullulanase-encoding gene, pulSL3 , was cloned from Alkalibacterium sp. SL3 and expressed in Escherichia coli. Deduced PulSL3 contains 2026 amino acid residues and consists of a putative signal peptide, four carbohydrate-binding modules, an E_set pullulanase domain, an α-amylase domain, and a pullulanase domain. The purified rPulSL3 exhibited pullulanase activity only. To identify the functions of the α-amylase and pullulanase domains, the N- and C-terminus truncated mutants (pulSL3△N and pulSL3△C) were also expressed in E. coli. The purified rPulSL3△N had pullulanase activity, while rPulSL3△C had no either α-amylase or pullulanase activity. Both rPulSL3 and rPulSL3△N exhibited maximum activities at pH 9.0 and 50 °C, and were highly active and stable at the concentration of NaCl up to 4 M and resistant to a few surfactants and detergents. In comparison to the wild type, rPulSL3△N had better thermostability (retaining 62.9 vs. 33.6% activity at 52 °C for 30 min), higher substrate affinity (with K m of 0.10 vs. 0.15 mg mL−1) and higher catalytic efficiency (836.6 vs. 520.3 mL mg−1 s−1). These excellent properties make rPulSL3△N potential for the application in the industries of detergent, food, and environmental remediation. [ABSTRACT FROM AUTHOR]

Viruses could rapidly diversify into variants, which has long been known to facilitate viral adaption in the host. Recent studies showed that cooperation among variants and wild-type (WT) also increased viral fitness. Here, a mutant of sC69∗ in small hepatitis B surface protein (SHBs) that resulted in premature stop was investigated and the frequency of sC69∗ was 4.37% (19/435), most of which coexisted with the WT (78.95%, 15/19), indicating mixed viral populations. Functional studies showed that sC69∗ mutant was associated with lower viral spread, but could be rescued by coexisting with the WT. The sC69∗ mutant showed to attenuate host innate immune response during infection and poly (I:C) treatment such as IL29, ISG15, and RIG-I (p < 0.05). The lower immune response was not caused by the lower replication of sC69∗ mutant. Our data provide information that sC69∗ coexisting with the WT might facilitate the fitness and persistence of the viral quasispecies in the host.

Viruses could rapidly diversify into variants, which has long been known to facilitate viral adaption in the host. Recent studies showed that cooperation among variants and wild-type (WT) also increased viral fitness. Here, a mutant of sC69∗ in small hepatitis B surface protein (SHBs) that resulted in premature stop was investigated and the frequency of sC69∗ was 4.37% (19/435), most of which coexisted with the WT (78.95%, 15/19), indicating mixed viral populations. Functional studies showed that sC69∗ mutant was associated with lower viral spread, but could be rescued by coexisting with the WT. The sC69∗ mutant showed to attenuate host innate immune response during infection and poly (I:C) treatment such as IL29, ISG15, and RIG-I (p < 0.05). The lower immune response was not caused by the lower replication of sC69∗ mutant. Our data provide information that sC69∗ coexisting with the WT might facilitate the fitness and persistence of the viral quasispecies in the host. [ABSTRACT FROM AUTHOR]

Bacterial expression is commonly used to produce recombinant and truncated mutant eukaryotic proteins. However, heterologous protein expression may render synthesized proteins insoluble. The conventional method used to express a poorly soluble protein, which involves denaturation and refolding, is time-consuming and inefficient. There are several non-denaturing approaches that can increase the solubility of recombinant proteins that include using different bacterial cell strains, altering the time of induction, lowering the incubation temperature, and employing different detergents for purification. In this study, we compared several non-denaturing protocols to express and purify two insoluble 34 kDa actin-bundling protein mutants. The solubility of the mutant proteins was not affected by any of the approaches except for treatment with the detergent sarkosyl. These results indicate that sarkosyl can effectively improve the solubility of insoluble proteins during bacterial expression. [ABSTRACT FROM AUTHOR]

The protein elicitor MoHrip2, which was extracted from Magnaporthe oryzae as an exocrine protein, triggers the tobacco immune system and enhances blast resistance in rice. However, the detailed mechanisms by which MoHrip2 acts as an elicitor remain unclear. Here, we investigated the structure of MoHrip2 to elucidate its functions based on molecular structure. The 3-dimensional structure of MoHrip2 was obtained. Overall, the crystal structure formed a β-barrel structure and showed high similarity to the pathogenesis-related (PR) thaumatin superfamily protein thaumatin-like xylanase inhibitor (TL-XI). To investigate the functional regions responsible for MoHrip2 elicitor activities, the full length and 8 truncated proteins were expressed in Escherichia coli and were evaluated for elicitor activity in tobacco. Biological function analysis showed that MoHrip2 triggered the defense system against Botrytis cinerea in tobacco. Moreover, only MoHrip2M14 and other fragments containing the 14 amino acids residues in the middle region of the protein showed the elicitor activity of inducing a hypersensitive response and resistance related pathways, which were similar to that of full-length MoHrip2. These results revealed that the central 14 amino acid residues were essential for anti-pathogenic activity.

NKX2.5 plays important roles in heart development. Being a transcription factor, NKX2.5 exerts its biological functions in nucleus. However, the sequence motif that localize NKX2.5 into nucleus is still not clear. Here, we found a R/K-rich sequence motif from Q187 to R197 (QNRRYKCKRQR) was required for exclusive nuclear localization of NKX2.5. Eight truncated plasmids (E109X, Q149X, Q170X, Q187X, Q198X, Y256X, Y259X, and C264X) which were associated with congenital heart disease (CHD) were constructed. Compared with the wild type NKX2.5, the proteins E109X, Q149X, Q170X, Q187X without intact homeodomain (HD) showed no transcriptional activity while Q198X, Y256X, Y259X and C264X with intact HD showed 50 to 66% transcriptional activity. E109X, Q149X, Q170X, Q187X without intact HD localized in the cytoplasm and nucleus simultaneously and Q198X, Y256X, Y259X and C264X with intact HD localized completely in nucleus. These results inferred the indispensability of 187 QNRRYKCKRQR 197 in exclusive nucleus localization. Additionally, this sequence motif was very conservative among human, mouse and rat, indicating this motif was important for NKX2.5 function. Thus, we concluded that R/K-rich sequence motif 187 QNRRYKCKRQR 197 played a central role for NKX2.5 nuclear localization. Our findings provided a clue to understand the mechanisms between the truncated NKX2.5 mutants and CHD. [ABSTRACT FROM AUTHOR]

We generated novel truncated insulin-like growth factor I receptors (IGF-IRs) designated as 126/STOP, 223/STOP and 325/STOP in order to establish shorter soluble IGF-IRs than previously reported 486/STOP without abrogating the same antitumor effects. Stable transfection of 223/STOP and 325/STOP, but not 126/STOP caused inhibition of anchorageindependent growth of CaOV-3 ovarian cancer cells in vitro. This antitumor effect was reproduced when we used recombinant proteins of these constructs, suggesting a bystander effect of these shorter truncated IGF-IRs. Tumorigenesis in vivo of CaOV-3 cells tranfected with 223/STOP or 325/STOP was strictly inhibited, and inoculation of these cells in nude mice caused massive apoptosis exclusively in vivo. Phosphorylations of IGF-IR and Akt, but not Erk were attenuated in 223/STOP- or 325/STOP-transfected CaOV-3 cells and downregulations of IGF-IR and Akt phosphorylation seemed to play at least a partial role in the antitumor effect of these novel truncated IGF-IRs. Since 223/STOP and 325/STOP are smaller in size than previously reported 486/STOP, and they retain the same antitumor effects, they could be good candidates for clinical application in the future. [ABSTRACT FROM AUTHOR]

Abstract: CueO is a multicopper oxidase (MCO) that is involved in the homeostasis of Cu in Escherichia coli and is the sole cuprous oxidase to have ever been found. Differing from other MCOs, the substrate-binding site of CueO is deeply buried under a methionine-rich helical region including α-helices 5, 6, and 7 that interfere with the access of organic substrates. We deleted the region Pro357–His406 and replaced it with a Gly-Gly linker. The crystal structures of a truncated mutant in the presence and in the absence of excess Cu(II) indicated that the scaffold of the CueO molecule and metal-binding sites were reserved in comparison with those of CueO. In addition, the high thermostability of the protein molecule and its spectroscopic and magnetic properties due to four Cu centers were also conserved after truncation. As for functions, the cuprous oxidase activity of the mutant was reduced to ca 10% that of recombinant CueO owing to the decrease in the affinity of the labile Cu site for Cu(I) ions, although activities for laccase substrates such as 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), p-phenylenediamine, and 2,6-dimethoxyphenol increased due to changes in the access of these organic substrates to the type I Cu site. The present engineering of CueO indicates that the methionine-rich α-helices function as a barrier to the access of bulky organic substrates, which provides CueO with specificity as a cuprous oxidase. [Copyright &y& Elsevier]

Maintenance of Ca2+ homeostasis is essential for normal cellular function and survival. Recent evidences suggest that Ca2+ is also an important player of apoptosis. We demonstrated that the plasma membrane Ca2+ ATPase (PMCA) isoform 4b, a key element of cellular Ca2+ homeostasis, was cleaved by caspase-3 during the course of apoptosis. This cleavage of PMCA removed the entire regulatory region from the C terminus, leaving behind a 120-kDa catalytic fragment. Since loss of PMCA activity could lead to intracellular Ca2+ overload and consequently necrotic cell death, an important question is whether the apoptotic fragment of PMCA retains full activity or it is inactivated. To address this question, we constructed a C-terminally truncated mutant that corresponded to the caspase-3 fragment of PMCA4b and showed that it was fully and constitutively active. This mutant was targeted properly to the plasma membrane when it was expressed stably or transiently in several different cell lines. We followed truncation of PMCA during apoptosis induced by mitochondrial or receptor-mediated pathways and found that a similar fragment of 120 kDa was formed and remained intact for several hours after treatment. We have also demonstrated that the caspase-3 cleavage site is an important structural element of PMCA and found that the accessibility of the caspase-3 site depended strongly on the conformational state of the protein. [ABSTRACT FROM AUTHOR]

A truncated mutant α-amylase, Xa-S2, was obtained from Xanthomonas campestris wild type α-amylases (Xa-WT) through random mutagenesis that contained 167 amino acid residues (approx 65% shorter than that of Xa-WT). Secondary structure prediction implied that Xa-S2, would be unable to form the whole (β/α)8-barrel catalytic domain and did not have the three conserved catalytic residues of wild type α-amylase, but it still displays the starch-hydrolyzing activity. Xa-S2 was prepared, characterized and compared to the recombinant wild-type enzymes. The K m for starch was 32 mg/ml; activity was optimal at pH 6.2 and 30°C. In contrast, the K m for starch of Xa-WT was 8 mg/ml and optimal enzyme activity was at pH 6.0–6.2 and 45–50°C. Our results suggested that Xa-S2 is a new amylase with a minimal catalytic domain for hydrolyzing substrates with of α-1,4-glucosidic bonds. [ABSTRACT FROM AUTHOR]

The ∈ subunit of the chloroplast AlP synthase and the truncated ∈ mutants which lack some amino acid residues from the N-terminus or C-terminus were overexpressed in E. coli. When the ∈ subunit or the truncated ∈ proteins was added to the spinach chloroplast suspension, both the intensity of the fast phase of millisecond delayed light emission (ms-DLE) and the cyclic and noncyclic photophosphorylation activity of chloroplast were enhanced. With an increase in the number of residues deleted from the N-terminus, the enhancement effect of the N-terminal truncated proteins decreased gradually. For the C-terminal truncated proteins, the enhancement effect increased gradually with an increase in the number of residues deleted from the C-terminus. Besides, the ATP synthesis activity of ∈-deficient membrane reconstituted with the ∈ subunit or the truncated ∈ proteins was compared. The ATP synthesis activity of reconstituted membrane with the N-terminal truncated proteins decreased gradually as the number of residues deleted from the N-terminus increased. For the C-terminal truncated proteins, the ATP synthesis activity of reconstituted membrane increased gradually with an increase in the number of residues deleted from the C-terminus, but was still lower than that of the wild type ∈ protein. These results suggested that: (a) the N-terminal domain of the ∈ subunit of the chloroplast ATP synthase could affect the ATP synthesis activity of ATP synthase by regulating the efficiency of blocking proton leakage of ∈ subunit; and (b) the C-terminal domain of the ∈ subunit of the chloroplast ATP synthase had a subtle function in modulating the ATP synthesis ability of ATP synthase. [ABSTRACT FROM AUTHOR]

Sequence alignment of human T-lymphotropic virus type I (HTLV-I) protease and other retroviral proteases reveals that the leukemia virus proteases contain residues at the C-terminus that are absent in the other proteases. We have prepared a mutant of HTLV-I protease that does not contain the 10 C-terminal residues and demonstrated that the catalytic efficiency of cleavage of a peptide substrate is unaffected. [Copyright &y& Elsevier]