Modelling of auxin-binding protein 1 suggests that its C-terminus and auxin could compete for a binding site that incorporates a metal ion and tryptophan residue 44

Auxin Binding Protein 57 (ABP57) is one of the molecular components involved in rice response to abiotic stress. The ABP57 gene encodes an auxin receptor which functions in activating the plasma membrane H+-ATPase. Biochemical properties of ABP57 have been characterized; however, the function of ABP57, particularly on stress and hormone responses is still limited. This study was conducted to understand the regulation of ABP57 expression under abiotic stress. Thus, in silico identification of cis-acting regulatory elements (CAREs) in the promoter region of ABP57 was performed. Several motifs and transcription factor binding site (TFBS) that are involved in abiotic stress such as ABRE, DRE, AP2/EREBP, WRKY and NAC were identified. Next, expression analysis of ABP57 under drought, salt, auxin (IAA) and abscisic acid (ABA) was conducted by reverse transcription-PCR (RT-PCR) to verify the effect of these treatments on ABP57 transcript level. ABP57 was expressed at different levels in the shoot and root under drought conditions, and its expression was increased under IAA and ABA treatments. Moreover, our results showed that ABP57 expression in the root was more responsive to drought, auxin and ABA treatments compared to its transcript in the shoot. This finding suggests that ABP57 is a drought-responsive gene and possibly regulated by IAA and ABA.

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Progesterone Receptor Membrane Component-1 (PGRMC1) Is the Mediator of Progesterone’s Antiapoptotic Action in Spontaneously Immortalized Granulosa Cells As Revealed by PGRMC1 Small Interfering Ribonucleic Acid Treatment and Functional Analysis of PGRMC1 Mutations

Endocrinology ◽

10.1210/en.2007-1050 ◽

2007 ◽

Vol 149 (2) ◽

pp. 534-543 ◽

Cited By ~ 123

Author(s):

John J. Peluso ◽

Jonathan Romak ◽

Xiufang Liu

Keyword(s):

Binding Site ◽

Rna Binding ◽

Transmembrane Domain ◽

Binding Protein ◽

Plasminogen Activator Inhibitor ◽

Membrane Receptor ◽

Membrane Component ◽

Plasminogen Activator Inhibitor 1 ◽

Receptor Membrane ◽

C Terminus

Progesterone (P4) receptor membrane component-1 (PGRMC1) and its binding partner, plasminogen activator inhibitor 1 RNA binding protein (PAIRBP1) are thought to form a complex that functions as membrane receptor for P4. The present investigations confirm PGRMC1’s role in this membrane receptor complex by demonstrating that depleting PGMRC1 with PGRMC1 small interfering RNA results in a 60% decline in [3H]P4 binding and the loss of P4’s antiapoptotic action. Studies conducted on partially purified GFP-PGRMC1 fusion protein indicate that [3H]P4 specifically binds to PGRMC1 at a single site with an apparent Kd of about 35 nm. In addition, experiments using various deletion mutations reveal that the entire PGRMC1 molecule is required for maximal [3H]P4 binding and P4 responsiveness. Analysis of the binding data also suggests that the P4 binding site is within a segment of PGRMC1 that is composed of the transmembrane domain and the initial segment of the C terminus. Interestingly, PAIRBP1 appears to bind to the C terminus between amino acids 70–130, which is distal to the putative P4 binding site. Taken together, these data provide compelling evidence that PGRMC1 is the P4 binding protein that mediates P4’s antiapoptotic action. Moreover, the deletion mutation studies indicate that each domain of PGRMC1 plays an essential role in modulating PGRMC1’s capacity to both bind and respond to P4. Additional studies are required to more precisely delineate the role of each PGRMC1 domain in transducing P4’s antiapoptotic action.

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