Ennis H L, Giorda R, Ohmachi T, Shaw D R, Blume J E
Roche Institute of Molecular Biology, Roche Research Center, Nutley, NJ 07110.
Dev Genet. 1991;12(1-2):133-8. doi: 10.1002/dvg.1020120121.
Two different cDNA clones denoted pTO270-6 and pTO270-11 represent two mRNAs that are developmentally regulated during spore germination in Dictyostelium discoideum. The respective mRNAs are found only during early germination and are not present in other stages of growth or multicellular development. Four different genomic clones that hybridize to sequences that are common to both of the 270 cDNA clones were isolated from Dictyostelium libraries and sequenced. Two are the genes for the two cDNAs, and the other two represent genes that do not seem to be transcribed. All four genomic sequences possess a very unusual internal feature in the deduced protein sequences composed of a monotonous repeat of the tetrapeptide threonine-glutamic acid-threonine-proline. The other portions of the proteins have no homology among themselves. The deduced protein corresponding to the 270-6 gene is very similar to avocado (Persea americana) cellulase. Since cellulose in the spore wall has to be digested during spore germination this suggests that this protein may function as an endo-(1,4)-beta-D-glucanase during germination.
两个不同的cDNA克隆，分别命名为pTO270 - 6和pTO270 - 11，代表了两种在盘基网柄菌孢子萌发过程中受到发育调控的mRNA。相应的mRNA仅在萌发早期出现，在生长或多细胞发育的其他阶段不存在。从盘基网柄菌文库中分离出四个与270 cDNA克隆共有的序列杂交的不同基因组克隆并进行测序。其中两个是两个cDNA的基因，另外两个代表似乎不被转录的基因。所有四个基因组序列在推导的蛋白质序列中都具有一个非常不寻常的内部特征，由苏氨酸 - 谷氨酸 - 苏氨酸 - 脯氨酸四肽的单调重复组成。蛋白质的其他部分彼此之间没有同源性。与270 - 6基因对应的推导蛋白质与鳄梨（Persea americana）纤维素酶非常相似。由于孢子壁中的纤维素在孢子萌发过程中必须被消化，这表明该蛋白质在萌发过程中可能作为一种内切 -（1,4）-β - D - 葡聚糖酶发挥作用。
