A low temperature induced apoplastic protein isolated from Arachis hypogaea

We describe the isolation, characterization and identification of an Arachi s hypogaea cold shock protein (AHCSP33). AHCSP33 is secreted into the leaf apoplast during law temperature exposure. N-terminal sequence of AHCSP33 sh ows homology to Thaumatin-Like (TTL) protein family (also called Group5 Pat hogenesis-related (PR) proteins). AHCSP33 shows strongest homology (55%) at the N-terminus with the Rye TL protein (M-r 25 k) which is an apoplastic p rotein and has antifreeze activity. Like several TL proteins, AHCSP33 is al so targeted to the apoplast and persists for several days after low tempera ture treatment, although at reduced levels. AHCSP33 possesses intrachain di sulfide bonds which is a well conserved feature of TL proteins. AHCSP33 mig ht be involved in cryoprotecting proteins as it was shown to prevent freeze -induced denaturation of L-lactate dehydrogenase (LDH). Several features of AHCSP33 are consistent with its role in cryoprotection. It is a hydrophili c protein and is boiling stable. Hydrophilic amino acids constitute 80.4 mo l%. Asp/Asn and Glu/Gln together constitute 20.8 mol%. AHCSP33 is glycosyla ted and exists as an oligomer in its native state. (C) 1998 Elsevier Scienc e Ltd. All rights reserved.