Nucleotide sequence and chromosomal location of Cab11 and Cab12, the genes for the fourth polypeptide of the photosystem I light-harvesting antenna (LHCI).

Tryptic peptide sequences from the 22 kDa polypeptide of tomato LHCI were used to construct a probe for gene cloning. The two genes cloned, cab11 and cab12, encode proteins of 251 and 250 residues that are 88% identical in overall amino acid sequence and 93% identical in the deduced mature protein. Each gene is present in a single copy per haploid genome; cab11 on chromosome 3 and cab12 on chromosome 6, and each has 2 introns located in similar positions to introns in other members of the Chl a/b-binding (CAB) protein gene family. Comparison of the amino acid sequences of LHCI, LHCII, CP29 and CP24 polypeptides confirms that all CABs share two regions of very high similarity which include the first and third transmembrane helices and the stroma-exposed sequences preceding them. However, near the N-terminus and between the conserved regions, the LHCI polypeptides have sequence motifs which appear to be PSI-specific.