COMPARISON OF TWO-HEXMERIC HEMOCYANIN STRUCTURES FROM CHELICERATA AND CRUSTACEA AT SUB-DOMAIN RESOLUTION

Felix de Haas, Jan F.L. van Breeman, Martha M.C. Bijlholt and Ernst F.J. van Bruqqcn

Our ultimate goal is the structural analysis of the interhexameric contacts in the multi-hexameric hemocyanins (Hc) of chelicerata and crustacea at the ievel of the amino acids involved. WC started to study the two-hexameric half Hc molecule from Eurypelma californicum (tarantula) and tKe two-hexameric whole Hc molecule from Cancer paqurus (north sea crab). Application of the multi- variate statisticai analysis (MSA) pro- cedure resulted in two distinct views for the averaged two-hexameric struc- tures, which were different for Eurypel- ma and Cancer Hc respectively. Pro]ec- ~~ tions of the electron density map ofthe X-ray structure from Panulirus interrup- tus (spiny lobster) Hc at 0.32 nm reso- lution were used to find the mutual orlentatlons of the hexamers within the averaged images. After determination of the relative positions and orientation of the hexamers we Introduced the three- dimensional C,-backbone structure of Panuiirus Hc with computer graphics in order to determine the areas involved in the contact between the two hexaners. Contacts could be distinguished between sub-domain regions rich in r-helices and regions with higher ;,-strand content The difference in hexameric arrzngenect between Eurypelma and Cancer hemocyanin can be explained by stm hindrance of secondary structure elements present in crustacea hemocyanin but absent in chclicerdta hemocyanin.

AUTOMATIC DATA LOGGING ON THE CM MICROSCOPE

li . van Ham and W.m. Businq

i’hil;ps A;!aiLt;;di, tictr;n vctlL.2, fid.ii;;r.,;

i&L, 5600 !.lr> E:l!ui:,ir.~i;, “i;t, ?%rther 121:ds

On the TEM, micrographs are often taken quickly after optimising the re- cording conditions, especially when the specimen is beam-sensitive. As a conse- quence, essential information about the

operating conditions frequentiy 1s iost, unless the operator 1s very m,eticulous in writing down a full description OF the area of interest and the conditions used. Recording many operating condi- tions directly on the photographrc mat- erial has the disadvantage of reducrny the area available for the rmaqe itself. In additioll, putting an operator- entered description on the photographic plate wastes vaiuable time before the expcsure.

The CM series of TEM and TEMISTEM systems therefore provide on-line data- logging facilities, where a user- selected set of data is sent automati- cally to a prrnter for direct printout or to a Remote Controi computer for storing in a disc file. In the standard facility, the data are recorded together in blocks such as operating conditions, STEM recording parameters, iens cur- renis, etc.

A new program FDATA has been devel- oped for the Remote Control computer that allows the oeprator to choose any sinale parameter withrn any block for automatic recordinq. In addrtion, the program prompts the operator to add a line of text for each exposure after the exposure has been made. With this pro- qram even a forgetful ceprator will be able to obtain a reliable loq of ali necessary data. The proqram is re- leased as public domain software.

THE ANTIGEN-PRESENTING CELLS OF THE RAT LUNG

C.E.G. Havenith, A.J. Breedilk and E.C.M. Iloefsmit

The potential antigen-presenting cells of the iunq are dendritic cells (DC) and macrophages in the broncho- aiveoiar and interstitial compartments. Known from the iiterature is that alveolar macrophages are relatively; in- efficient in the performance of acces- sory cell activity. Also it has been described that DC are potent antigen- presentrng cells, probably playiny c role in presenting antigen in primary immune responses. In normal rats, pre- limiilary analysis of Ia antigen in the lur,q using indirect Lmmunoperoxidase staininq in liaht and electron micros-