Crystal structure of a ribonuclease from the seeds of bitter gourd (Momordica charantia) at 1.75 Å resolution

Nakagawa, Atsushi; Tanaka, Isao; Sakai, Ritsu; Nakashima, Takashi; Funatsu, Gunki; Kimura, Makoto

doi:10.1016/s0167-4838(99)00126-0

Cited by 30 publications

(16 citation statements)

References 24 publications

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“…Six structures related to human RNase T2 derived from three different RNases were investigated: RNase LE from tomato Solanum lycopersicum (20), Ribonuclease MC from bitter gourd Momordica charantia (38,39) and Ribonuclease NW from Nicotiana glutinosa (40). A secondary structure matching superposition of all three proteins with human RNase T2 revealed that the core fold is strictly conserved, while the outer loops show conformational differences.…”

Section: Resultsmentioning

confidence: 99%

Structure and activity of the only human RNase T2

Thorn

Steinfeld

Ziegenbein

et al. 2012

Nucleic Acids Research

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Mutations in the gene of human RNase T2 are associated with white matter disease of the human brain. Although brain abnormalities (bilateral temporal lobe cysts and multifocal white matter lesions) and clinical symptoms (psychomotor impairments, spasticity and epilepsy) are well characterized, the pathomechanism of RNase T2 deficiency remains unclear. RNase T2 is the only member of the Rh/T2/S family of acidic hydrolases in humans. In recent years, new functions such as tumor suppressing properties of RNase T2 have been reported that are independent of its catalytic activity. We determined the X-ray structure of human RNase T2 at 1.6 Å resolution. The α+β core fold shows high similarity to those of known T2 RNase structures from plants, while, in contrast, the external loop regions show distinct structural differences. The catalytic features of RNase T2 in presence of bivalent cations were analyzed and the structural consequences of known clinical mutations were investigated. Our data provide further insight into the function of human RNase T2 and may prove useful in understanding its mode of action independent of its enzymatic activity.

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Section: Resultsmentioning

confidence: 99%

Structure and activity of the only human RNase T2

Thorn

Steinfeld

Ziegenbein

et al. 2012

Nucleic Acids Research

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“…2). The electron density map for S 3 - (32), RNase LE in yellow (33), and RNase MC1 in green (34). c, stereo drawing of the space filling model of S 3 -RNase.…”

Section: Resultsmentioning

confidence: 99%

Crystal Structure at 1.5-Å Resolution of Pyrus pyrifolia Pistil Ribonuclease Responsible for Gametophytic Self-incompatibility

Matsuura¹,

Sakai²,

Unno³

et al. 2001

Journal of Biological Chemistry

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The crystal structure of the Pyrus pyrifolia pistil ribonuclease (S 3 -RNase) responsible for gametophytic selfincompatibility was determined at 1.5-Å resolution. It consists of eight helices and seven ␤-strands, and its folding topology is typical of RNase T 2 family enzymes. Based on a structural comparison of S 3 -RNase with RNase Rh, a fungal RNase T 2 family enzyme, the active site residues of S 3 -RNase assigned were His 33 and His 88 as catalysts and Glu 84 and Lys 87 as stabilizers of an intermediate in the transition state. Moreover, amino acid residues that constitute substrate binding sites of the two RNases could be superimposed geometrically. A hypervariable (HV) region that has an S-allele-specific sequence comprises a long loop and short ␣-helix. This region is far from the active site cleft, exposed on the molecule's surface, and positively charged. Four positively selected (PS) regions, in which the number of nonsynonymous substitutions exceeds that of synonymous ones, are located on either side of the active site cleft, and accessible to solvent. These structural features suggest that the HV or PS regions may interact with a pollen S-gene product(s) to recognize self and non-self pollen.Many flowering plants have a self-incompatibility system that recognizes the self or non-self between the pistil and pollen (tube) after pollination and suppresses growth of the self-pollen tube to prevent self-fertilization (1, 2). Gametophytic self-incompatibility (GSI) 1 is controlled genetically by a single locus (S-locus) with multiple alleles (1, 2). When a pollen grain lands on a stigma of the pistil, a process that discriminates as to whether an S-allele of the pollen matches one of the two Salleles of the pistil takes place. The pollen grain germinates on the stigma and grows into the style toward the embryo. If its S-allele matches one of the two S-alleles of the pistil, pollen tube growth is arrested in the style, and no fertilization takes place. In solanaceous, scrophulariaceous, and rosaceous plants that have GSI, the pistil glycoproteins that cosegregate with the S-alleles have been identified as ribonucleases of the RNase T 2 family (S-RNase) (3). McClure et al. (4) reported that pollen rRNA is degraded after self-pollination but not after crosspollination and suggested that GSI expression is mediated by degradation of the pollen rRNA of self-pollen tubes by S-RNase, leading to depletion of protein biosynthesis and the eventual arrest of tube growth. S-RNase has been confirmed necessary for GSI from results of gain-of-function and loss-of-function experiments on transgenic plants of solanaceous species (5, 6). Transgenic experiments also have shown that the RNase activity of S-RNase is necessary for GSI (7), which in petunia the carbohydrate moiety is not responsible for GSI (8), and that mutant S-RNase, which has lost RNase activity, acts as a dominant negative for GSI (9).Based on these findings, two models have been proposed to explain S-allele-specific inhibition of pollen tube growth; the...

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“…The elucidation of the crystal structure of a plant member of this family, i.e., RNase LE from tomato, revealed the presence of five disulfide bonds, two of which are conserved in all RNase T 2 enzymes, another two are conserved in the animal/plant subfamily, and the remaining disulfide bond appears to be unique to RNase LE (Tanaka et al, 2000). The first four bonds described are also conserved with those identified in the S 2 -RNase of Nicotiana alata and in RNase Mc1 of Momordica charantia (bitter gourd) (Oxley and Bacic, 1996;Nakagawa et al, 1999). The presence of conserved disulfide bonds in plant RNases suggests the possibility that they may be required for RNase conformational stability and/ or activity.…”

Section: Introductionmentioning

confidence: 83%

RNase activity requires formation of disulfide bonds and is regulated by the redox state

2004

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The activity of many RNases requires the formation of one or more disulfide bonds which can contribute to their stability. In this study, we show that RNase activity and, to a much lesser extent, nuclease activity, are redox regulated. Intracellular RNase activity was altered in vitro by changes in the glutathione redox state. Moreover, RNase activity was abolished following exposure to reducing agents such as beta-ME or DTT. Following reduction with glutathione (GSH), RNase activity could be fully reactivated with oxidized glutathione (GSSG). In contrast, RNase activity could not be reactivated when reduced with DTT. Decreasing the level of glutathione in vivo in wheat increased RNase activity. Tobacco engineered to have an increased glutathione redox state exhibited substantially lower RNase activity during dark-induced senescence. These results suggest that RNase activity requires the presence of one or more disulfide bonds that are regulated by glutathione and demonstrate for the first time that RNase activity can be altered with an alteration in cellular redox state.

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Crystal structure of a ribonuclease from the seeds of bitter gourd (Momordica charantia) at 1.75 Å resolution

Cited by 30 publications

References 24 publications

Structure and activity of the only human RNase T2

Structure and activity of the only human RNase T2

Crystal Structure at 1.5-Å Resolution of Pyrus pyrifolia Pistil Ribonuclease Responsible for Gametophytic Self-incompatibility

RNase activity requires formation of disulfide bonds and is regulated by the redox state

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