| First Author | Chen B | Year | 1999 |
| Journal | Mol Biol Cell | Volume | 10 |
| Issue | 12 | Pages | 4327-39 |
| PubMed ID | 10588661 | Mgi Jnum | J:58991 |
| Mgi Id | MGI:1350756 | Doi | 10.1091/mbc.10.12.4327 |
| Citation | Chen B, et al. (1999) Espin contains an additional actin-binding site in its N terminus and is a major actin-bundling protein of the Sertoli cell-spermatid ectoplasmic specialization junctional plaque. Mol Biol Cell 10(12):4327-39 |
| abstractText | The espins are actin-binding and -bundling proteins localized to parallel actin bundles. The 837-amino-acid 'espin' of Sertoli cell-spermatid junctions (ectoplasmic specializations) and the 253-amino-acid 'small espin' of brush border microvilli are splice isoforms that share a C-terminal 116-amino-acid actin-bundling module but contain different N termini. To investigate the roles of espin and its extended N terminus, we examined the actin-binding and -bundling properties of espin constructs and the stoichiometry and developmental accumulation of espin within the ectoplasmic specialization. An espin construct bound to F-actin with an approximately threefold higher affinity (K(d) = approximately 70 nM) than small espin and was approximately 2.5 times more efficient at forming bundles. The increased affinity appeared to be due to an additional actin-binding site in the N terminus of espin. This additional actin-binding site bound to F-actin with a K(d) of approximately 1 microM, decorated actin stress fiber-like structures in transfected cells, and was mapped to a peptide between the two proline-rich peptides in the N terminus of espin. Espin was detected at approximately 4-5 x 10(6) copies per ectoplasmic specialization, or approximately 1 espin per 20 actin monomers and accumulated there coincident with the formation of parallel actin bundles during spermiogenesis. These results suggest that espin is a major actin-bundling protein of the Sertoli cell-spermatid ectoplasmic specialization. |
