Structure of plant Photosystem I-plastocyanin complex reveals strong hydrophobic interactions

Photosystem I is defined as plastocyanin-ferredoxin oxidoreductase. Taking advantage of genetic engineering, kinetic analyses and cryo-EM, our data provide novel mechanistic insights into binding and electron transfer between PSI and Pc. Structural data at 2.74 Å resolution reveals strong hydrophobic interactions in the plant PSI-Pc ternary complex, leading to exclusion of water molecules from PsaA-PsaB / Pc interface once the PSI-Pc complex forms. Upon oxidation of Pc, a slight tilt of bound oxidized Pc allows water molecules to accommodate the space between Pc and PSI to drive Pc dissociation. Such a scenario is consistent with the six times larger dissociation constant of oxidized as compared to reduced Pc and mechanistically explains how this molecular machine optimized electron transfer for fast turnover.

Structure of plant PSI-plastocyanin complex reveals strong hydrophobic interactions

Photosystem I is defined as plastocyanin-ferredoxin oxidoreductase. Taking advantage of genetic engineering, kinetic analyses and cryo-EM, our data provide novel mechanistic insights into binding and electron transfer between PSI and Pc. Structural data at 2.74 Å resolution reveals strong hydrophobic interactions in the plant PSI-Pc ternary complex, leading to exclusion of water molecules from PsaA-PsaB / Pc interface once the PSI-Pc complex forms. Upon oxidation of Pc, a slight tilt of bound oxidized Pc allows water molecules to accommodate the space between Pc and PSI to drive Pc dissociation. Such a scenario is consistent with the six times larger dissociation constant of oxidized as compared to reduced Pc and mechanistically explains how this molecular machine optimized electron transfer for fast turnover.One Sentence SummaryGenetic engineering, kinetics and cryo-EM structural data reveal a mechanism in a major step of oxygenic photosynthesis

Circulating oxidized LDL, increased in patients with acute myocardial infarction, is accompanied by heavily modified HDL

Oxidized LDL (oxLDL) is a known risk factor for atherogenesis. This study aimed to reveal structural features of oxLDL present in human circulation related to atherosclerosis. When LDL was fractionated on an anion-exchange column, in vivo-oxLDL, detected by the anti-oxidized PC (oxPC) mAb, was recovered in flow-through and electronegative LDL [LDL(−)] fractions. The amount of the electronegative in vivo-oxLDL, namely oxLDL in the LDL(−) fraction, present in patients with acute MI was 3-fold higher than that observed in healthy subjects. Surprisingly, the LDL(−) fraction contained apoA1 in addition to apoB, and HDL-sized particles were observed with transmission electron microscopy. In LDL(−) fractions, acrolein adducts were identified at all lysine residues in apoA1, with only a small number of acrolein-modified residues identified in apoB. The amount of oxPC adducts of apoB was higher in the LDL(−) than in the L1 fraction, as determined using Western blotting. The electronegative in vivo-oxLDL was immunologically purified from the LDL(−) fraction with an anti-oxPC mAb. The majority of PC species were not oxidized, whereas oxPC and lysoPC did not accumulate. Here, we propose that there are two types of in vivo-oxLDL in human circulating plasma and the electronegative in vivo-oxLDL accompanies oxidized HDL.

Oxidative Changes in Cerebral Spinal Fluid Phosphatidylcholine during Treatment for Acute Lymphoblastic Leukemia

Central nervous system (CNS) treatment contributes to improved long-term disease-free survival from childhood acute lymphoblastic leukemia (ALL) by sigificantly decreasing the rate of disease relapse. Methotrexate (MTX), a drug commonly used for CNS treatment, has been associated with cognitive and academic problems, white-matter changes, perfusion defects, and brain atrophy. This study investigated oxidative stress as a possible mechanism of chemotherapyinduced CNS injury. Unoxidized and oxidized components of phosphatidylcholine (PC), the most prevalent phospholipid in CNS cellular membranes, were measured in cerebral spinal fluid (CSF) samples obtained from 21 children diagnosed with low (n = 7), standard (n= 7), or high (n= 7) risk ALL. Children with high-risk ALL received the most MTX, especially during the most intensive phase of treatment (consolidation). Phospholipids were extracted from CSF samples obtained at diagnosis and during the induction, consolidation, and continuation treatment phases. Unoxidized and oxidized PC were measured by normalphase high-performance liquid chromatography at 2 ultraviolet wavelengths (206 and 234 nm, respectively). Data were analyzed by 2-way repeated-measures analysis of variance. Results support the hypotheses that the highest levels of oxidized PC would be observed during the most intensive phase of ALL therapy and in the high-risk ALL group. Findings provide preliminary evidence for chemotherapy-induced oxidative stress inCNSmembrane phospholipids.