The RST and PARP-like domain containing SRO protein family: analysis of protein structure, function and conservation in land plants.
BACKGROUND
The SROs (SIMILAR TO RCD-ONE) are a group of plant-specific proteins which have important functions in stress adaptation and development. They contain the catalytic core of the poly(ADP-ribose) polymerase (PARP) domain and a C-terminal RST (RCD-SRO-TAF4) domain. In addition to these domains, several, but not all, SROs contain an N-terminal WWE domain.


RESULTS
SROs are present in all analyzed land plants and sequence analysis differentiates between two structurally distinct groups; cryptogams and monocots possess only group I SROs whereas eudicots also contain group II. Group I SROs possess an N-terminal WWE domain (PS50918) but the WWE domain is lacking in group II SROs. Group I domain structure is widely represented in organisms as distant as humans (for example, HsPARP11). We propose a unified nomenclature for the SRO family. The SROs are able to interact with transcription factors through the C-terminal RST domain but themselves are generally not regulated at the transcriptional level. The most conserved feature of the SROs is the catalytic core of the poly(ADP-ribose) polymerase (PS51059) domain. However, bioinformatic analysis of the SRO PARP domain fold-structure and biochemical assays of AtRCD1 suggested that SROs do not possess ADP-ribosyl transferase activity.


CONCLUSIONS
The SROs are a highly conserved family of plant specific proteins. Sequence analysis of the RST domain implicates a highly preserved protein structure in that region. This might have implications for functional conservation. We suggest that, despite the presence of the catalytic core of the PARP domain, the SROs do not possess ADP-ribosyl transferase activity. Nevertheless, the function of SROs is critical for plants and might be related to transcription factor regulation and complex formation.
Plant Biology Division, Department of Biosciences, University of Helsinki, Viikinkaari 1, FI-00014 Helsinki, Finland.
Pinja
P
Jaspers
Kirk
K
Overmyer
Michael
M
Wrzaczek
Julia P
JP
Vainonen
Tiina
T
Blomster
Jarkko
J
Salojärvi
Ramesha A
RA
Reddy
Jaakko
J
Kangasjärvi
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics; D017124:Conserved Sequence; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics*; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics; D054730:Protein Interaction Domains and Motifs; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D013329:Structure-Activity Relationship; D014157:Transcription Factors / Q000378:metabolism
D010940:Plant Proteins; D014157:Transcription Factors; D011065:Poly(ADP-ribose) Polymerases