RESUMO
Protein design is able to create artificial proteins with advanced functions, and computer simulation plays a key role in guiding the rational design. In the absence of structural evidence for cytoglobin (Cgb) with an intramolecular disulfide bond, we recently designed a de novo disulfide bond in myoglobin (Mb) based on structural alignment (i.e., V21C/V66C Mb double mutant). To provide deep insight into the regulation role of the Cys21-Cys66 disulfide bond, we herein perform molecular dynamics (MD) simulation of the fluoride-protein complex by using a fluoride ion as a probe, which reveals detailed interactions of the fluoride ion in the heme distal pocket, involving both the distal His64 and water molecules. Moreover, we determined the kinetic parameters of fluoride binding to the double mutant. The results agree with the MD simulation and show that the formation of the Cys21-Cys66 disulfide bond facilitates both fluoride binding to and dissociating from the heme iron. Therefore, the combination of theoretical and experimental studies provides valuable information for understanding the structure and function of heme proteins, as regulated by a disulfide bond. This study is thus able to guide the rational design of artificial proteins with tunable functions in the future.
Assuntos
Fluoretos/metabolismo , Mutação , Parvalbuminas/química , Parvalbuminas/metabolismo , Sítios de Ligação , Cristalografia por Raios X , Citoglobina/química , Dissulfetos/química , Humanos , Modelos Moleculares , Simulação de Dinâmica Molecular , Parvalbuminas/genética , Ligação Proteica , Conformação ProteicaRESUMO
A de novo designed intramolecular disulfide bond in myoglobin, resembling that in cytoglobin without structural evidence, was confirmed by an X-ray structure for the first time and was demonstrated to regulate both the structure and function of this protein, which fulfills the design of an artificial dehaloperoxidase, with an activity exceeding that of a native enzyme.
Assuntos
Dissulfetos/química , Globinas/química , Mioglobina/química , Peroxidases/química , Engenharia de Proteínas , Sítios de Ligação , Catálise , Cristalografia por Raios X , Citoglobina , Heme/química , Humanos , Mutação , Mioglobina/genética , Alinhamento de SequênciaRESUMO
To investigate the dynamic fluctuation of terpenoid relevant transcriptomics in transgenic ARTEMISIA ANNUA plants that express the genomic integrated antisense squalene synthase gene ( ASSS), we have quantified the transcript levels of the sterol anabolic SS gene as well as artemisinin biogenetic amorphadiene synthase (ADS), cytochrome P450 monooxygenase (CYP71AV1) and cytochrome P450 reductase (CPR) genes by real-time fluorescent quantitative polymerase chain reaction (RFQ-PCR). The SS mRNA level in transgenic plants sharply droped to 7.4 % - 55.3 % (i. e., 44.7 - 92.6 % reduction as the wild-type control), strongly implying that the expression of endogenous SS gene is significantly suppressed by the exogenous ASSS gene. In a synchronous fashion, ADS, CYP71AV1 and CPR mRNA levels elevated with the decline of SS mRNA level in transgenic plants, and the maximal ADS, CYP71AV1 and CPR mRNA levels in transgenic plants were 3.0-, 4.4- and 2.5-fold, respectively, higher than those in the control. Without a lethal effect but with a distinguishable impact on the organogenesis and morphology of transgenic plants, the down-regulation of SS gene has also led to the coordinated overexpression of ADS, CYP71AV1 and CPR genes together with the overproduction of artemisinin although no fully perfect correlation among the available experimental data has been shown.