Mouse-Torpedo hybrid acetylcholine receptors: functional homology does not equal sequence homology.
AUTOR(ES)
White, M M
RESUMO
The nicotinic acetylcholine (AcCho) receptor (AcChoR) is a multisubunit protein complex of stoichiometry alpha 2 beta gamma delta. The several subunits show homology with each other within a given species; in addition, homology is found between analogous subunits between species. We have used the phage SP6 RNA polymerase transcription system to produce single-species RNA in vitro for various AcChoR subunits from cDNAs. Injection of an equimolar mixture of RNA for the alpha, beta, gamma, and delta subunits of Torpedo californica AcChoR into Xenopus oocytes results in the appearance of functional receptors in the oocyte membrane. No response to AcCho is detected when the beta or gamma subunit RNA is omitted, and a small response is seen when the delta subunit RNA is omitted. Replacement of Torpedo delta subunit RNA by the mouse BC3H-1 cell line AcChoR delta subunit RNA leads to the formation of functional receptors that show a 3-4-fold greater response to AcCho than does the full Torpedo complex. No response is seen when the mouse delta RNA replaces Torpedo gamma RNA. By amino acid homology profile comparisons, the mouse delta subunit appears to be moderately but not highly similar to the Torpedo delta subunit; the apparent similarity to the Torpedo gamma subunit is only slightly less. Therefore, the features of the primary sequence that determine the functional delta character of the mouse polypeptide are not revealed by simple homology comparisons.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=391003Documentos Relacionados
- Meiotic disjunction of circular minichromosomes in yeast does not require DNA homology.
- The human kappa deleting element and the mouse recombining segment share DNA sequence homology.
- Malformation syndromes: a review of mouse/human homology.
- Low-level inversion of the L component of pseudorabies virus is not dependent on sequence homology.
- Comparison of cloned mouse alpha- and beta-globin genes: conservation of intervening sequence locations and extragenic homology.