NUCLEOTIDE-SEQUENCE OF THE SECY GENE FROM LACTOCOCCUS-LACTIS AND IDENTIFICATION OF CONSERVED REGIONS BY COMPARISON OF 4 SECY PROTEINS

SecY is an integral membrane protein which participates in the translocation of proteins through the bacterial cell membrane. We have cloned the secY gene of Lactococcus lactis, and found its deduced protein sequence, 439 amino acids long, to be similar in length to the previously determined SecY proteins of Escherichia coli, Bacillus subtilis and Mycoplasma capricolum. Comparison of the L. lactis SecY to the 3 other SecY proteins revealed 90 conserved amino acid residues (21%). Nearly half of the conserved residues are clustered in 2 of the 10 transmembrane segments, and in 2 of the 6 cytoplasmic regions. Some of the conserved regions are apparently responsible for the interactions of SecY with signal sequences, and the proteins SecE and SecA.