skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Plant Protein O-Arabinosylation
A wide range of proteins with diverse functions in development, defense, and stress responses are O -arabinosylated at hydroxyprolines (Hyps) within distinct amino acid motifs of continuous stretches of Hyps, as found in the structural cell wall extensins, or at non-continuous Hyps as, for example, found in small peptide hormones and a variety of plasma membrane proteins involved in signaling. Plant O -glycosylation relies on hydroxylation of Prolines to Hyps in the protein backbone, mediated by prolyl-4-hydroxylase (P4H) which is followed by O -glycosylation of the Hyp C 4 -OH group by either galactosyltransferases (GalTs) or arabinofuranosyltranferases (Ara f Ts) yielding either Hyp-galactosylation or Hyp-arabinosylation. A subset of the P4H enzymes with putative preference to hydroxylation of continuous prolines and presumably all Ara f T enzymes needed for synthesis of the substituted arabinose chains of one to four arabinose units, have been identified and functionally characterized. Truncated root-hair phenotype is one common denominator of mutants of Hyp formation and Hyp-arabinosylation glycogenes, which act on diverse groups of O -glycosylated proteins, e.g., the small peptide hormones and cell wall extensins. Dissection of different substrate derived effects may not be regularly feasible and thus complicate translation from genotype to phenotype. Recently, lack of proper arabinosylation on arabinosylated proteins has been shown to influence their transport/fate in the secretory pathway, hinting to an additional layer of functionality of O -arabinosylation. Here, we provide an update on the prevalence and types of O -arabinosylated proteins and the enzymatic machinery responsible for their modifications.  more » « less
Award ID(s):
1755482
PAR ID:
10219634
Author(s) / Creator(s):
; ;
Date Published:
Journal Name:
Frontiers in Plant Science
Volume:
12
ISSN:
1664-462X
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; (, The Plant Journal)
    Summary HYDROXYPROLINEO‐ARABINOSYLTRANSFERASEs (HPATs) initiate a post‐translational protein modification (Hyp‐Ara) found abundantly on cell wall structural proteins. InArabidopsis thaliana,HPAT1andHPAT3are redundantly required for full pollen fertility. In addition to the lack of Hyp‐Ara inhpat1/3pollen tubes (PTs), we also found broadly disrupted cell wall polymer distributions, particularly the conversion of the tip cell wall to a more shaft‐like state. Mutant PTs were slow growing and prone to rupture and morphological irregularities. In a forward mutagenesis screen for suppressors of thehpat1/3low seed‐set phenotype, we identified a missense mutation inexo70a2, a predicted member of the vesicle‐tethering exocyst complex. The suppressed pollen had increased fertility, fewer morphological defects and partially rescued cell wall organization. A transcriptional null allele ofexo70a2also suppressed thehpat1/3fertility phenotype, as did mutants of core exocyst complex membersec15a, indicating that reduced exocyst function bypassed the PT requirement for Hyp‐Ara. In a wild‐type background,exo70a2reduced male transmission efficiency, lowered pollen germination frequency and slowed PT elongation. EXO70A2 also localized to the PT tip plasma membrane, consistent with a role in exocyst‐mediated secretion. To monitor the trafficking of Hyp‐Ara modified proteins, we generated an HPAT‐targeted fluorescent secretion reporter. Reporter secretion was partially dependent onEXO70A2and was significantly increased inhpat1/3PTs compared with the wild type, but was reduced in the suppressedexo70a2 hpat1/3tubes. 
    more » « less
  2. ; (, Plants)
    All living cells generate structurally complex and compositionally diverse spectra of glycans and glycoconjugates, critical for organismal evolution, development, functioning, defense, and survival. Glycosyltransferases (GTs) catalyze the glycosylation reaction between activated sugar and acceptor substrate to synthesize a wide variety of glycans. GTs are distributed among more than 130 gene families and are involved in metabolic processes, signal pathways, cell wall polysaccharide biosynthesis, cell development, and growth. Glycosylation mainly takes place in the endoplasmic reticulum (ER) and Golgi, where GTs and glycosidases involved in this process are distributed to different locations of these compartments and sequentially add or cleave various sugars to synthesize the final products of glycosylation. Therefore, delivery of these enzymes to the proper locations, the glycosylation sites, in the cell is essential and involves numerous secretory pathway components. This review presents the current state of knowledge about the mechanisms of protein trafficking between ER and Golgi. It describes what is known about the primary components of protein sorting machinery and trafficking, which are recognition sites on the proteins that are important for their interaction with the critical components of this machinery. 
    more » « less
  3. ; ; (, Proteins: Structure, Function, and Bioinformatics)
    Abstract Structures at serine‐proline sites in proteins were analyzed using a combination of peptide synthesis with structural methods and bioinformatics analysis of the PDB. Dipeptides were synthesized with the proline derivative (2S,4S)‐(4‐iodophenyl)hydroxyproline [hyp(4‐I‐Ph)]. The crystal structure of Boc‐Ser‐hyp(4‐I‐Ph)‐OMe had two molecules in the unit cell. One molecule exhibitedcis‐proline and a type VIa2 β‐turn (BcisD). Thecis‐proline conformation was stabilized by a C–H/O interaction between Pro C–Hαand the Ser side‐chain oxygen. NMR data were consistent with stabilization ofcis‐proline by a C–H/O interaction in solution. The other crystallographically observed molecule hadtrans‐Pro and both residues in the PPII conformation. Two conformations were observed in the crystal structure of Ac‐Ser‐hyp(4‐I‐Ph)‐OMe, with Ser adopting PPII in one and the β conformation in the other, each with Pro in the δ conformation andtrans‐Pro. Structures at Ser‐Pro sequences were further examined via bioinformatics analysis of the PDB and via DFT calculations. Ser‐Pro versus Ala–Pro sequences were compared to identify bases for Ser stabilization of local structures. C–H/O interactions between the Ser side‐chain Oγand Pro C–Hαwere observed in 45% of structures with Ser‐cis‐Pro in the PDB, with nearly all Ser‐cis‐Pro structures adopting a type VI β‐turn. 53% of Ser‐trans‐Pro sequences exhibited main‐chain COi•••HNi+3or COi•••HNi+4hydrogen bonds, with Ser as theiresidue and Pro as thei + 1 residue. These structures were overwhelmingly either type I β‐turns or N‐terminal capping motifs on α‐helices or 310‐helices. These results indicate that Ser‐Pro sequences are particularly potent in favoring these structures. In each, Ser is in either the PPII or β conformation, with the Ser Oγcapable of engaging in a hydrogen bond with the amide N–H of thei + 2 (type I β‐turn or 310‐helix; Serχ1t) ori + 3 (α‐helix; Serχ1g+) residue. Non‐prolinecisamide bonds can also be stabilized by C–H/O interactions. 
    more » « less
  4. ; (, Org. Biomol. Chem.)
    Bacteria can produce gibberellin plant hormones. While the bacterial biosynthetic pathway is similar to that of plants, the individual enzymes are very distantly related and arose via convergent evolution. The cytochromes P450 (CYPs) that catalyze the multi-step oxidation of the alkane precursor ent -kaurene ( 1 ) to ent -kauren-19-oic acid ( 5 ), are called ent -kaurene oxidases (KOs), and in plants are from the CYP701 family, and share less than 19% amino acid sequence identity with those from bacteria, which are from the phylogenetically distinct CYP117 family. Here the reaction series catalyzed by CYP117 was examined by 18 O 2 labeling experiments, the results indicate successive hydroxylation of 1 to ent -kauren-19-ol ( 2 ) and then ent -kauren-19,19-diol ( 3 ) and most likely an intervening dehydration to ent -kauren-19-al ( 4 ) prior to the concluding hydroxylation to 5 . Accordingly, the bacterial and plant KOs converged on catalysis of the same series of reactions, despite their independent evolutionary origin. 
    more » « less
  5. ; ; ; ; ; ; ; ; ; (, Stem Cell Reports)
    Undifferentiated neural stem and progenitor cells (NSPCs) encounter extracellular signals that bind plasma membrane proteins and influence differentiation. Membrane proteins are regulated by N-linked glycosylation, making it possible that glycosylation plays a critical role in cell differentiation. We assessed enzymes that control N-glycosylation in NSPCs and found that loss of the enzyme responsible for generating β1,6-branched N-glycans, N-acetylglucosaminyltransferase V (MGAT5), led to specific changes in NSPC differentiation in vitro and in vivo. Mgat5 homozygous null NSPCs in culture formed more neurons and fewer astrocytes compared with wild-type controls. In the brain cerebral cortex, loss of MGAT5 caused accelerated neuronal differentiation. Rapid neuronal differentiation led to depletion of cells in the NSPC niche, resulting in a shift in cortical neuron layers in Mgat5 null mice. Glycosylation enzyme MGAT5 plays a critical and previously unrecognized role in cell differentiation and early brain development. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email