THE NUCLEOTIDE-SEQUENCE OF THE GENE FOR MALF PROTEIN, AN INNER MEMBRANE COMPONENT OF THE MALTOSE TRANSPORT-SYSTEM OF ESCHERICHIA-COLI - REPEATED DNA-SEQUENCES ARE FOUND IN THE MALE-MALF INTERCISTRONIC REGION

Abstract

The malF gene product is an inner membrane component of the maltose transport system in E. coli. Some gene fusions between malF and lacZ (encoding the normally cytoplasmic enzyme .beta.-galactosidase) produce hybrid proteins which are membrane-bound, while other fusions produce hybrid proteins which are cytoplasmic. To further analyze the localization properties of the different classes of malF-lacZ fusion proteins and of the intact MalF protein, the DNA sequence of 5 malF-lacZ fusions and the wild type malF gene were determined. From the predicted amino acid sequence, MalF protein contains 514 amino acids and has a MW of 56,947. Analysis of the hydropathic character of MalF using the Kyte-Doolittle assignments indicates that the protein may have 2 or 3 amino-terminal membrane-spanning segments and 4 or 5 carboxy-terminal membrane-spanning segments separated by a region of 181 hydrophilic residues. Localization properties of the different fusion proteins correspond with degree of hydrophobicity. By sequencing upstream from malF, the malF-malF intercistronic region was found to be 153 base pairs in length and to contain inverted repeats, homologous to intercistronic repeats of many other persons. Further analysis of this region may help in understanding the observed step-down in synthesis of the MalF protein.