Crystal structure of alr1298, a pentapeptide repeat protein from Nostoc Pcc 7120, determined at 2.3 Angstrom resolution

Experimental Data Snapshot

  • Resolution: 2.27 Å
  • R-Value Free: 0.251 
  • R-Value Work: 0.199 
  • R-Value Observed: 0.204 

wwPDB Validation   3D Report Full Report

This is version 1.2 of the entry. See complete history


Crystal structure of Alr1298, a pentapeptide repeat protein from the cyanobacterium Nostoc sp. PCC 7120, determined at 2.1 angstrom resolution.

Zhang, R.Ni, S.Kennedy, M.A.

(2020) Proteins 88: 1143-1153

  • DOI: https://doi.org/10.1002/prot.25882
  • Primary Citation of Related Structures:  
    6OMX, 6UV7, 6UVI

  • PubMed Abstract: 

    Nostoc sp. PCC 7120 are filamentous cyanobacteria capable of both oxygenic photosynthesis and nitrogen fixation, with the latter taking place in specialized cells known as heterocysts that terminally differentiate from vegetative cells under conditions of nitrogen starvation. Cyanobacteria have existed on earth for more than 2 billion years and are thought to be responsible for oxygenation of the earth's atmosphere. Filamentous cyanobacteria such as Nostoc sp. PCC 7120 may also represent the oldest multicellular organisms on earth that undergo cell differentiation. Pentapeptide repeat proteins (PRPs), which occur most abundantly in cyanobacteria, adopt a right-handed quadrilateral β-helical structure, also referred to as a repeat five residue (Rfr) fold, with four-consecutive pentapeptide repeats constituting a single coil in the β-helical structure. PRPs are predicted to exist in all compartments within cyanobacteria including the thylakoid and cell-wall membranes as well as the cytoplasm and thylakoid periplasmic space. Despite their intriguing structure and importance to understanding ancient cyanobacteria, the biochemical function of PRPs in cyanobacteria remains largely unknown. Here we report the crystal structure of Alr1298, a PRP from Nostoc sp. PCC 7120 predicted to reside in the cytoplasm. The structure displays the typical right-handed quadrilateral β-helical structure and includes a four-α-helix cluster capping the N-terminus and a single α-helix capping the C-terminus. A gene cluster analysis indicated that Alr1298 may belong to an operon linked to cell proliferation and/or thylakoid biogenesis. Elevated alr1298 gene expression following nitrogen starvation indicates that Alr1298 may play a role in response to nitrogen starvation and/or heterocyst differentiation.

  • Organizational Affiliation

    Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Alr1298 protein
A, B
187Nostoc sp. PCC 7120 = FACHB-418Mutation(s): 0 
Gene Names: alr1298
Find proteins for Q8YXB7 (Nostoc sp. (strain PCC 7120 / SAG 25.82 / UTEX 2576))
Explore Q8YXB7 
Go to UniProtKB:  Q8YXB7
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ8YXB7
Sequence Annotations
  • Reference Sequence
Small Molecules
Modified Residues  1 Unique
IDChains TypeFormula2D DiagramParent
Query on MSE
A, B
Experimental Data & Validation

Experimental Data

  • Resolution: 2.27 Å
  • R-Value Free: 0.251 
  • R-Value Work: 0.199 
  • R-Value Observed: 0.204 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 45.842α = 90
b = 86.363β = 90
c = 96.047γ = 90
Software Package:
Software NamePurpose
XDSdata collection
Aimlessdata scaling

Structure Validation

View Full Validation Report

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2020-03-04
    Type: Initial release
  • Version 1.1: 2020-03-11
    Changes: Database references
  • Version 1.2: 2020-08-12
    Changes: Database references