Proteins Associated with the Carbon Dioxide Concentrating Mechanism of Chlamydomonas reinhardtii

单细胞藻类，包括莱茵衣藻， 在体内浓缩二氧化碳的能力， 在CO2浓度低于 大多数高等植物都能忍受。 二氧化碳浓度 机制是诱导型的;它只存在于具有 在有限的二氧化碳条件下生长。 的一个重要方面 这个Ci（Ci = CO2 + HCO 3- + CO 3 -2）成藏体系位于 在叶绿体中。 从低CO2- 成长C。莱因哈德氏细胞保留了积累Ci的能力， 比从高密度脂蛋白中分离的完整叶绿体的含量高得多， 二氧化碳培养的细胞 五种多肽特异性诱导 在低CO2条件下生长，而在高CO2需求条件下则缺失 已鉴定出菌株CIA-5。 其中一种蛋白质是 碳酸酐酶位于周质间隙，另一个位于细胞质间隙。 是一种36 kDa的膜相关多肽，位于完整的 叶绿体 其他三种蛋白质是可溶性的， 功能未知。 叶绿体在CI中的作用 积累的特征是通过测定 来自野生型和高CO2需要C. reinhardtii菌株 36 kDa多肽在此过程中的作用 吸收过程也在调查中。 这种蛋白质 位于叶绿体上，可能在叶绿体被膜中， 并且可能部分负责增加Ci摄取， 在低CO2培养的叶绿体中观察到。 的 叶绿体碳酸酐酶低丰度，组成型 制造的蛋白质是有效的二氧化碳固定所需的， 被研究。 其他三个低CO2诱导的作用 多肽未知。 一个cDNA文库正在被制作成mRNA 从低CO2生长的细胞中分离并进行差异筛选 用来自低浓度和高浓度CO2培养的细胞的mRNA制成的cDNA。 这 将确定许多低CO2诱导基因所需的 低CO2增长。 蛋白质的最终特征 这一运输系统将增加我们对 藻类的低CO2调节作用及叶绿体在 这种光合作用的适应。 光合作用包括二氧化碳的光合作用 (CO2)以及光致氧（O2）的释放。 部分原因是 植物的气体交换活动， 从一个高二氧化碳和低氧气的组成， 氧气含量高二氧化碳含量低 在目前情况下， CO2固定率和因此植物生长，可以限制 二氧化碳。 许多单细胞藻类可以适应低二氧化碳条件， 他们在利用二氧化碳方面变得非常有效， 光合作用 这种适应是增强 细胞运输和积累无机碳的能力。 这些研究表征了蛋白质组分所需的 二氧化碳在绿色温室中的有效利用 莱因哈德氏菌 重点放在叶绿体的作用 无机碳的获取。

Unicellular algae, including Chlamydomonas reinhardtii, have the capacity to concentrate CO2 internally, allowing these organisms to grow photoautotrophically at CO2 concentrations lower than most higher plants can tolerate. This CO2 concentrating mechanism is inducible; it is present only in cells that have been grown with limiting CO2 conditions. An important aspect of this Ci (Ci = CO2 + HCO3- + CO3-2) accumulation system is located in the chloroplast. Intact chloroplasts isolated from low CO2- grown C. reinhardtii cells retain the ability to accumulate Ci to much higher levels than intact chloroplasts isolated from high Co2-grown cells. Five polypeptides that are specifically induced by growth on low CO2 and are missing in the high CO2-requiring strain CIA-5 have been identified. One of these proteins is a carbonic anhydrase located in the periplasmic space and another is a 36 kDa membrane associated polypeptide located in intact chloroplasts. The other three proteins are soluble and their function is unknown. The role of the chloroplast in Ci accumulation is being characterized by determining Ci uptake in intact chloroplasts from wild-type and high CO2-requiring C. reinhardtii strains. The role of the 36 kDa polypeptide in this uptake process is also being investigated. This protein is located on the chloroplast, possibly in the chloroplast envelope, and may be responsible, in part, for the increase in Ci uptake observed in chloroplasts from low CO2-grown cultures. The chloroplast carbonic anhydrase a low abundance, constitutively made protein that is required for efficient CO2 fixation is also being studied. The role of the three other low CO2-induced polypeptides is unknown. A cDNA library is being made to mRNA isolated from low CO2-grown cells and differentially screened with cDNA made from mRNA from low and high CO2-grown cells. This will identify many of the low CO2-inducible genes required for growth on low CO2. The eventual characterization of the proteins of this transport system will increase our understanding of the low CO2 adjustment in algae and the role of the chloroplast in this photosynthetic adaptation. Photosynthesis involves the photoassimilation of carbon dioxide (CO2) and the photoevolution of oxygen (O2). Partly due to this gas exchange activity of plants, earth's atmosphere changed in composition from one that was high in CO2 and low in O2 to one that is high in O2 and low in CO2. Under current conditions, the rate of CO2 fixation and thus plant growth, can be limited by CO2. Many unicellular algae can adapt to low CO2 conditions so that they become very efficient in their utiliation of CO2 for photosynthesis. This adaptation results from an enhancement of the cells' ability to transport and accumulate inorganic carbon. These studies characterize the protein components required for the efficient use of CO2 in the green alga Chlamydomonas reinhardtii. Emphasis is placed on the role of the chloroplast in inorganic carbon acquisition.