In the cyanobacterium Synechocystis sp. PCC 6803 five open reading frames (scpA–scpE) have been identified that code for single-helix proteins resembling helices I and III of chlorophyll a/b-binding (Cab) antenna proteins from higher plants. They have been named SCPs (small Cab-like proteins). Deletion of a single scp gene in a wild-type or in a photosystem I-less (PS I-less) strain has little effect. However, the effects of functional deletion of scpB or scpE were remarkable under conditions where chlorophyll availability was limited. When cells of a strain lacking PS I and chlL (coding for a polypeptide needed for light-independent protochlorophyllide reduction) were grown in darkness, the phycobilin and protochlorophyllide levels decreased upon deletion of scpB or scpE and the protoheme level was reduced in the strain lacking scpE. Addition of δ-aminolevulinic acid (ALA) in darkness drastically increased the level of Mg-protoporphyrin IX and Mg-protoporphyrin IX monomethyl ester in the PS I-less/chlL −/scpE − strain, whereas PChlide accumulated in the PS I-less/chlL −/scpB − strain. In the PS I-less/chlL − control strain ALA supplementation did not lead to large changes in the levels of tetrapyrrole biosynthesis intermediates. We propose that ScpE and ScpB regulate tetrapyrrole biosynthesis as a function of pigment availability. This regulation occurs primarily at an early step of tetrapyrrole biosynthesis, prior to ALA. In view of the conserved nature of chlorophyll-binding sites in these proteins, it seems likely that regulation by SCPs occurs as a function of chlorophyll availability, with SCPs activating chlorophyll biosynthesis steps when they do not have pigments bound.
Plant Molecular Biology – Springer Journals
Published: Oct 13, 2004
It’s your single place to instantly
discover and read the research
that matters to you.
Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.
All for just $49/month
Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly
Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.
Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.
Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.
All the latest content is available, no embargo periods.
“Hi guys, I cannot tell you how much I love this resource. Incredible. I really believe you've hit the nail on the head with this site in regards to solving the research-purchase issue.”Daniel C.
“Whoa! It’s like Spotify but for academic articles.”@Phil_Robichaud
“I must say, @deepdyve is a fabulous solution to the independent researcher's problem of #access to #information.”@deepthiw
“My last article couldn't be possible without the platform @deepdyve that makes journal papers cheaper.”@JoseServera