Structure and expression of a pea nuclear gene encoding a chlorophyll a/b-binding polypeptide

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Abstract
A nuclear gene AB80 was isolated from a phage .lambda. Charon 4 library of pea DNA. The sequence of the gene was determined and it contained an uninterrupted reading frame of 269 amino acids, corresponding to a precursor to a constituent polypeptide of the light-harvesting chlorophyll a/b-protein complex. Primer extension and S1 nuclease studies defined a cap site for AB80. The 1st methionine codon 3'' from this site is 69 nucleotides away and is the initiating codon of the open reading frame. A "TATA" sequence occurs 31 nucleotides 5'' from the cap site. A 2nd TATA sequence is found 7 nucleotides on the 5'' side of the initiating methionine codon and the sequences surrounding this TATA sequence are strikingly similar to those surrounding the 1st TATA sequence. The mature polypeptide encoded by AB80 differs by 5 amino acids from the polypeptide corresponding to a previously characterized cDNA [complementary DNA] sequence pAB96. This result is indicative of heterogeneity within the constituent polypeptides of the light-harvesting chlorophyll a/b-protein complex. The sequence Arg-Lys-Ser-Ala-Thr-Thr-Lys-Lys occurs at, or near, the NH2-terminus of the mature polypeptide encoded by AB80. This basic peptide is of interest because of its apparent involvement in changes in excitation-energy distribution in chloroplast membranes. Some general similarities, but no extensive sequence homology, is found on comparing the transit sequence for the precursor to the chlorophyll a/b-binding polypeptide with the transit sequences previously determined for the precursors to the small subunit of ribulose-1,5-bisphosphate carboxylase.