Structural modules for receptor dimerization in the S-locus receptor kinase extracellular domain.
In: Proceedings of the National Academy of Sciences of the United States of America, Jg. 104 (2007-07-17), Heft 29, S. 12211-6
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Zugriff:
The highly polymorphic S-locus receptor kinase (SRK) is the stigma determinant of specificity in the self-incompatibility response of the Brassicaceae. SRK spans the plasma membrane of stigma epidermal cells, and it is activated in an allele-specific manner on binding of its extracellular region (eSRK) to its cognate pollen coat-localized S-locus cysteine-rich (SCR) ligand. SRK, like several other receptor kinases, forms dimers in the absence of ligand. To identify domains in SRK that mediate ligand-independent dimerization, we assayed eSRK for self-interaction in yeast. We show that SRK dimerization is mediated by two regions in eSRK, primarily by a C-terminal region inferred by homology modeling/fold recognition techniques to assume a PAN_APPLE-like structure, and secondarily by a region containing a signature sequence of the S-domain gene family, which might assume an EGF-like structure. We also show that eSRK exhibits a marked preference for homodimerization over heterodimerization with other eSRK variants and that this preference is mediated by a small, highly variable region within the PAN_APPLE domain. Thus, the extensive polymorphism exhibited by the eSRK not only determines differential affinity toward the SCR ligand, as has been assumed thus far, but also underlies a previously unrecognized allelic specificity in SRK dimerization. We propose that preference for SRK homodimerization explains the codominance exhibited by a majority of SRKs in the typically heterozygous stigmas of self-incompatible plants, whereas an increased propensity for heterodimerization combined with reduced affinity of heterodimers for cognate SCRs might underlie the dominant-recessive or mutual weakening relationships exhibited by some SRK allelic pairs.
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Structural modules for receptor dimerization in the S-locus receptor kinase extracellular domain.
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Autor/in / Beteiligte Person: | Naithani, S ; Chookajorn, T ; Ripoll, DR ; Nasrallah, JB |
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Zeitschrift: | Proceedings of the National Academy of Sciences of the United States of America, Jg. 104 (2007-07-17), Heft 29, S. 12211-6 |
Veröffentlichung: | Washington, DC : National Academy of Sciences, 2007 |
Medientyp: | academicJournal |
ISSN: | 0027-8424 (print) |
DOI: | 10.1073/pnas.0705186104 |
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