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Characterization of the Arabidopsis At5-MMP Matrix Metalloproteinase
Tang Guozhu,Wu Shuchi,Zhao Bingyu,Flinn Barry S. 한국식물학회 2022 Journal of Plant Biology Vol.65 No.6
The plant extracellular matrix (ECM) represents the continuum between the plasma membrane and the apoplast, and undergoes significant modifications during plant growth, development and stress responses. While matrix metalloproteinases (MMPs) are significant proteolytic modulators of the vertebrate ECM, they remain poorly understood in plant biology. Of the five Arabidopsis thaliana MMPs, At5-MMP is the most constitutively expressed and was chosen for further characterization. Autoactivation of recombinant At5-MMP generated a functional metalloproteinase which exhibited maximum proteolytic activity at pH 7.5, and a broad level of activity into the basic range. Furthermore, an E to A mutation within the HEIGH portion of the At5-MMP catalytic domain abolished proteolytic activity. Using GFP-tagged At5-MMP variants expressed in Nicotiana benthamiana, the predicted signal peptide was required for targeting to the cell periphery, and deletion of this peptide resulted in intracellular, localized At5-MMP accumulation. Using a generic MMP cleavage PXG(L/I) peptide sequence, the predicted Arabidopsis extracellular proteome was screened for potential candidate MMP substrates. The extracellular domain of one candidate, WAK1, was expressed as a recombinant protein and shown to be cleaved internally at specific sites by At5-MMP in vitro. These same cleavage sites were identified using mammalian MMP cleavage prediction software.
급냉응고 처리된 초내열 합금 A-286 의 기계적 성질 및 강화기구
이성학,신기삼,Kelly, Thomas F,Flinn, John E 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.3
Mechanical test data of superalloy A-286 show that there is a significant increase in tensile strength after rapid solidification processing (RSP). The mechanism of mechanical property improvement upon RSP was studied by TEM quantitative defect analysis and the data analysis using strengthening models. The most prominent microstructural alterations by RSP are found in the precipitates and in the grain growth behavior. On average, the precipitates in RSP samples are smaller, have higher volume fractions, and are much more stable than their conventionally processed counterparts. The increased tensile strength of the RSP samples is found to be the result of the increased volume fraction and number density of second phase particles. However, the strengthening came mostly through grain growth inhibition by the second phase particles, which in turn increased the strength via Hall-Petch relationship. This study shows the importance of recrystallization and thus the method of consolidation for effective strengthening.