Sinadinović J, Krancanić M, Jovanović M, Kostić G
Endokrinologie. 1976 Jun;67(2):204-14.
The dynamics of biosynthesis of thyroglobulin (TG) subunits and their polymerization were studied comparatively in rabbit and guinea-pig thyroid in vitro. The incorporation of 14C-leucine into soluble, microsome-bound proteins (total and per mg) and into various fractions of soluble proteins was followed during incubation for 5 to 300 minutes. Some differences in TG synthesis between rabbits and guinea-pigs were observed, namely in the dynamics of 14C-leucine incorporation, the rate of subunit aggregation, the relationship between soluble and particulate proteins and the sedimentation characteristics of newly synthesized and pre-formed TG. The incorporation of 14C-leucine into soluble and microsome-bound proteins increased with time of incubation, but in rabbits the level of incorporation was much higher than in guinea-pigs. In rabbits, the ratio between radioactivity in soluble and particulate proteins decreased with time. In guinea-pig, this ratio increased with time of incubation and was much higher than in rabbits. Sucrose density gradient analysis of the newly formed soluble proteins showed that 12S fraction was synthesized in relatively large amounts, during early incubation of rabbit thyroid, although it was no found as a native protein in the thyroid extract of this species. After prolonged incubation the quantity of 12S protein decreased with a simultaneous increase in the amount of newly formed TG. The quick transformation of 12S subunit into TG is probably the reason why native 12S protein is absent in rabbit thyroid gland. However, in guinea-pigs the transformation into TG is much slower so that a considerable amount of radioactivity remained in the 12S fraction even after 300 min incubation. The results from rabbit experiments suggest that the 12S protein, probably represents a precursor of TG. In guinea-pig, the origin of 12S protein is twofold, as subunit of TG and as a product of its dissociation.
在体外对兔和豚鼠甲状腺中甲状腺球蛋白（TG）亚基的生物合成动力学及其聚合过程进行了比较研究。在5至300分钟的孵育过程中，追踪了14C-亮氨酸掺入可溶性、微粒体结合蛋白（总量和每毫克）以及可溶性蛋白各组分的情况。观察到兔和豚鼠在TG合成方面存在一些差异，即在14C-亮氨酸掺入动力学、亚基聚集速率、可溶性蛋白与颗粒性蛋白的关系以及新合成和预先形成的TG的沉降特性方面。14C-亮氨酸掺入可溶性和微粒体结合蛋白的量随孵育时间增加，但兔中的掺入水平远高于豚鼠。在兔中，可溶性蛋白和颗粒性蛋白中的放射性比值随时间下降。在豚鼠中，该比值随孵育时间增加，且远高于兔。对新形成的可溶性蛋白进行蔗糖密度梯度分析表明，在兔甲状腺孵育早期，相对大量地合成了12S组分，尽管在该物种的甲状腺提取物中未发现其作为天然蛋白存在。长时间孵育后，12S蛋白的量减少，同时新形成的TG量增加。12S亚基快速转化为TG可能是兔甲状腺中不存在天然12S蛋白的原因。然而，在豚鼠中转化为TG的速度要慢得多，以至于即使孵育300分钟后，12S组分中仍保留相当量的放射性。兔实验结果表明，12S蛋白可能代表TG的前体。在豚鼠中，12S蛋白的来源是双重的，既是TG的亚基，也是其解离产物。
