The yeast Saccharomyces cerevisiae gene CCHl (ORF YGR217w) shows high homology with animal calcium channel al-subunit genes. Knock-out mutants were constructed of Cchl and of Midi which is known to mediate Ca 2+ influx in response to the a-mating pheromone. Cchl is involved in calcium influx and the late stage of the mating process. The cchl mutant sensitivity against the a-mating pheromone can be reduced by the addition of extra calcium. The product of this gene is likely to interact with the MIDI gene product in Ca influx or its control.

A soluble extract from pea (Pisum sativum L.) roots, when incubated with ATP and inositol 1,4,5-trisphosphate, produced an inositol tetrakisphosphate. The chromatographic properties of this inositol tetrakisphosphate, and of the products formed by its chemical degradation, identify it as inositol 1,4,5,6-tetrakisphosphate. No evidence was obtained for a 3-phosphorylation of inositol 1,4,5-trisphosphate. The importance of these observations with respect to inositol phosphates and calcium signalling in higher plants, is discussed.

Metabolism of the putative messenger molecule D-myo-inositol(1,4,5)trisphosphate [Ins(1,4,5) (4,5)P2). The hydrolysis of Ptdlns(4,5)P2 leads to a concomitant production of 1,2-diacylglycerol (DG) which activates protein kinase C (1). Several pieces of evidence for the structural presence of a similar signal transducing system (the phosphoinositide-or PI-system) in plant cells have emerged. These include the presence of: (a) phosphatidylinositol(4)phosphate and phosphatidylinositol (4,5)bisphosphate (2, 9, 13, 15); (b) kinases and phosphatases involved in polyphosphoinositide metabolism (9, 24); and (c) enzymes which in many respects resemble mammalian phosphoinositidase(s) C (19, 28) and protein kinase(s) C (10).Possible functional roles for the PI-system in processes such as light-induced, motor-cell activation in Samanea pulvini (21,22)

Much intcrest is currently directed towards amylin, a member of the calcitonin/calcitonin gene-related peptide Ahhrcvi;itions used: CGRP. calcitonin gene-related protein; BSA, hovine serum alhumin.(CGRP) family of peptides, this stems from its proposed involvement in the aetiology of type I1 diabetes. It has also been known for some time that the pancreas from noninsulin dependent diabetics contains deposits of amyloid, an extracellular protein matrix [ 11. The major peptide component of amyloid, known as amylin, has been purified and sequenced. It has 37 amino acids and a 46% sequence similarity with CGRP 121.Certain effects of arnylin have been observed which may have a direct bearing o n the pathology of diabetes, the most Vol. I x