This domain is found in the yeast cell wall assembly regulator Smi1 (also known as Knr4) [ (PUBMED:7937796) (PUBMED:8289782) ].
Saccharomyces cerevisiae Knr4 has a regulatory role in chitin deposition and in cell wall assembly [ (PUBMED:10206705) ]. It is believed to connect the PKC1-SLT2 MAPK pathway with cell proliferation. It has been shown to interact with Bck2, a gene involved in cell cycle progression in S. cerevisiae (forming a complex) to allow PKC1 to coordinate the cell cycle (cell proliferation) with cell wall integrity [ (PUBMED:12185498) (PUBMED:12823808) ]. Knr4 also interacts with the tyrosine-tRNA synthetase protein encoded by Tys1 and is involved in sporulation process [ (PUBMED:11410349) ].
Proteins containing this domain also include the animal F-box only protein 3 (FBXO3). In humans, FBXO3 is a substrate recognition component of the SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complex [ (PUBMED:18809579) ].
Interestingly, Smi1/Knr4 homologues from bacteria are potential immunity proteins in a subset of these contact-dependent inhibitory toxin systems [ (PUBMED:21306995) ].
Note: previously reported evidence that Knr4 may interact with nuclear matrix-association region [ (PUBMED:8516310) ] may be due to an artefact [ (PUBMED:10206705) ].
Family alignment:
There are 15672 SMI1_KNR4 domains in 15452 proteins in SMART's nrdb database.
Click on the following links for more information.
Evolution (species in which this domain is found)
Taxonomic distribution of proteins containing SMI1_KNR4 domain.
This tree includes only several representative species. The complete taxonomic breakdown of all proteins with SMI1_KNR4 domain is also avaliable.
Click on the protein counts, or double click on taxonomic names to display all proteins containing SMI1_KNR4 domain in the selected taxonomic class.
Cloning and characterization of a Neurospora crassa gene required for(1,3) beta-glucan synthase activity and cell wall formation.
Proc Natl Acad Sci U S A. 1994; 91: 9500-4
Display abstract
The glucan synthase 1 gene (gs-1) is required for (1,3) beta-glucansynthase activity [E.C. 2.4.1.34; UDP glucose:1,3-beta-D-glucan3-beta-D-glucosyltransferase] and for cell wall formation. The gs-1 genewas cloned by functional complementation of the cell-wall-less defect ofthe (1,3) beta-glucan synthase-deficient mutant, TM1, by using a genomicNeurospora crassa cosmid library. A 2568-nucleotide gs-1 cDNA sequencerevealed a 532-amino acid open reading frame encoding a polypeptide of 59kDa. The predicted gs-1 gene product has no obvious signal peptidecleavage sites or transmembrane domains. A gs-1 null mutant is defectivefor cell wall formation and (1,3) beta-glucan synthase activity. Thepredicted GS-1 protein is weakly homologous to a putative Saccharomycescerevisiae transcriptional regulatory protein.
Cloning and characterization of KNR4, a yeast gene involved in(1,3)-beta-glucan synthesis.
Mol Cell Biol. 1994; 14: 1017-25
Display abstract
k9 killer toxin from Hansenula mrakii was used to select a number ofresistant mutants from Saccharomyces cerevisiae. Preliminary biochemicaland genetic studies showed that some of them acquired structural defectsin the cell wall. One of these mutants, the knr4-1 mutant, displays anumber of cell wall defects, including osmotic sensitivity; sensitivity tocercosporamide, a known antifungal agent; and resistance to Zymolyase, a(1,3)-beta-glucanase. We report here the isolation and analysis of theKNR4 gene. DNA sequence analysis revealed an uninterrupted open readingframe which contains five potential start codons. The longest codingtemplate encodes a protein of 505 amino acids with a calculated molecularmass of 57,044 Da. A data base search revealed 100% identity with anuclear protein, SMI1p. Disruption of the KNR4 locus does not result incell death; however, it leads to reduced levels of both (1,3)-beta-glucansynthase activity and (1,3)-beta-glucan content in the cell wall. The genewas mapped to the right arm of chromosome VII.
