Shotgun proteomics analysis on maize chloroplast thylakoid membrane.

In this study we initiated a proteomic investigation of the maize thylakoid membrane by using a shotgun proteomic approach based on LC-MS(E). A total of 34 maize thylakoid membrane proteins were identified, the majority of which are primarily involved in photosynthesis, including the light-reaction and carbon assimilation. It is noteworthy that all of the core subunits of the Photosystem II were identified in our search. Proteins involved in other processes, such as iron storage, were also detected in our study. The quantity of each identified protein was also determined. Of interest, we discovered that the amount of the three ATP synthase subunits were not equivalent, suggesting that these proteins perform other functions in addition to ATP synthesis. To our knowledge this is the first extensive proteomic investigation of the maize thylakoid membrane, and will likely enable further study of maize photosynthesis and chloroplast development.

Identification of low abundance polyA-binding proteins in Arabidopsis chloroplast using polyA-affinity column.

Proteins could be well separated and further identified by the use of 2-DE and related techniques. Yet, there are many proteins could not be detected even by more effective dyes because of their inherent low abundance or their low resolution. As a result, polyA-affinity column was used as a method to enrich polyA-binding proteins and then identified by MALDI-TOF-MS. In this study, 23 Arabidopsis chloroplast protein spots coded by 18 genes were identified, and majority of these proteins were classified into three related categories according to their annotations in the Swiss-Prot database, including NAD-, RNA-, and ATP-binding motifs, respectively. The major goal of the present Arabidopsis chloroplast proteomics project was to identify novel polyA-binding proteins or protein isoforms located in Arabidopsis chloroplasts and the specific research of cellular proteins with extremely low transcription levels could be fulfilled.