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Summary: Thylakoid protein targeting: tat pathway. In E. coli, the pathway has 3 protein components: tatA, tatB and tatC. tha4 is the ortholog of bacterial tatA. A tha4 mutant allele is slightly pale green and seedling lethal due to decreased levels of many thylakoid proteins.
Image: mutant leaf color depicted on a seedling leaf color scale
First Defining Report: Walker et al. 1999
Key Allele
tha4-m1::Mu1; Mu1 insertion 35 bp upstream of the start codon. Slightly pale green, seedling lethal phenotype with occasional green sectors.
Map Location
Maps to long arm of chromosome 1 with chromosome B-A translocations (Walker et al 1999).
Gene Product
THA4, a homolog of bacterial tatA, is localized to thylakoid membranes. The pea THA4 ortholog forms a tranlocating membrane channel (Dabney-Smith and Cline 2009). The tat protein translocation pathway is trans-membrane, pH-gradient dependent, and SecA independent. In bacteria, it involves three protein components: tatA, tatB and tatC. A tatC component has not yet been defined in maize.
Related loci
hcf106, ortholog of the bacterial tatB component.
References
Dabney-Smith C, Cline K (2009) Clustering of C-terminal stromal domains of Tha4 homo-oligomers during translocation by the Tat protein transport system. Mol Biol Cell 20:2060-9. PUBMED
Walker MB, Roy LM, ColemanE, Voelker R, Barkan A (1999) The maize tha4 gene functions in Sec-independent protein transport in chloroplasts and is related to hcf106, tatA, and tatB. J Cell Biol 147: 267-276. PUBMED
Links: MGDB: tha4 NCBI: tha4 UniProt: Q9XFJ8