Open AccessDisulphide Bonding in a Stylar Self‐Incompatibility Ribonuclease of Nicotiana Alata
Author(s) -
Oxley David,
Bacic Antony
Publication year - 1996
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1996.0075r.x
Subject(s) - ribonuclease , rnase p , biology , locus (genetics) , allele , amino acid , genetics , stereochemistry , biochemistry , rna , chemistry , gene
Many flowering plants have developed a self‐incompatibility mechanism, which is controlled by a single polyallelic locus (the S ‐locus), to prevent inbreeding. The products of the S ‐locus in the styles of solanaceous plants are an allelic series of glycoproteins with RNase activity [McClure, B. A., Haring, V., Ebert, P. R., Anderson, M. A., Simpson, R. J., Sakiyama, F. & Clarke, A. E. (1989) Nature 342 , 955–957]. These S ‐RNases show some amino‐acid‐sequence similarity with two fungal RNases (T 2 and Rh), including the presence of two active‐site His residues, which suggests a common three‐dimensional structure. Disulphide bonding is important in the maintenance of the three‐dimensional structure of the fungal RNases [Kurihara, H., Mitsui, Y., Ohgi, K., Irie, M., Mizuno, H. & Nakamura, T. (1992) FEBS Lett. 306 , 189–192] and the S ‐RNases [Tsai, D. S., Lee, H.‐S., Post, L. C., Kreiling, K. M. & Kao, T.‐H. (1992) Sex. Plant Reprod. 5 , 256–263]. We have used the S 2 ‐allele RNase of Nicotiana alata , which has nine Cys residues, to establish the pattern of disulphide bonding. The disulphide bonds Cys16–Cys21, Cys45–Cys94, Cys153–Cys182 and Cys165–Cys176 are consistent with the S 2 ‐RNase having a similar three‐dimensional structure to RNase Rh. A free Cys residue (Cys95) adjacent to Cys45‐Cys94 promotes a rapid specific disulphide migration when the protein is exposed to denaturing conditions.