Characterization of a maize heat-shock protein 101 gene, HSP101, encoding a C1pB/Hsp100 protein homologue

Heat shock protein 101 (HSP101) cDNA and genomic clones from maize have bee n isolated. The structure of maize HSP101 reveals the presence of six exons interrupted by five introns. Maize HSP101 contains a predicted open readin g frame that translates into a 912-aa sequence with a mass of 101 kDa. Init iation of transcription was mapped 146 bases upstream of the AUG codon. Fiv e heat shock element (HSE) boxes were found within the proximal 289 bases o f the promoter region. Southern blot analysis of genomic DNA indicates that the maize genome contains only one copy of HSP101. A protein sequence comp arison showed that maize Hsp101 belongs to the heat shock 100 kDa and casei no-lytic protease B protein family (Hsp100/ClpB) that plays important roles in bacteria and yeast in the survival to extremely high temperatures and t he control of proteolysis. Accumulation of HSP101 mRNA was strong under hea t shock conditions, but not detectable after cold or osmotic stress treatme nts or by exogenous application of ABA. The analysis of the predicted super secondary structure of maize Hsp101 showed that a coiled-coil located in th e middle region of the protein is evolutionarily conserved in all members o f the Clp A, B and C subfamilies. It is proposed that these supersecondary structures may have important roles in Clp function. (C) 1999 Elsevier Scie nce B.V. All rights reserved.