There are genome sequences available for several species of Streptomyces. By aligning cellobiohydrolase genes of interest, you should be able to design degenerate PCR primers complementary to regions of high conservation. Or alternatively, just look at sending your Streptomyces isolate to a sequencing lab for genome sequencing.

The best way is the classical procedure. If the gene is coding for a mRNA start by purifying the mRNA and by means of reverse transcriptase synthesize the cDNA, then go on according to classical protocols...Look at the old protocol of Maniatis.

Dr. Roonan thanks for your answer i have already done this . i have alligned 19 genes and make primers from conserved regions . now have get the approx 900 bp fregment . i hv sequenced it and cross check . now this is My stucking point how to go for start and stop codon from this sequence to get Cbh gene sothat i may use it for cloning etc.... i can't afford to go for genomic sequenceing . kindly assist me in moving forward . thanks

For that you can use comparative analysis having closest similar organism from there you can collect the gene sequence and from there you can prepare degenerate primers to amplify the cellobiohydrolase of your Streptomyces sp.

I hope this may help.

Use RACE to amplify the gene.

You can use free online tools such as the NCBI's ORFfinder (https://www.ncbi.nlm.nih.gov/orffinder/) or propriety software such as Geneious's Find ORFs function to locate potential ORFs in your sequence and then compare with the codon lengths of known cellobiohydrolase genes in Streptomyces sp. That should give a good indication of your expected gene length but to confirm the start site, you would need to use RT-PCR and sequence the cDNA obtained for your gene. You can also express your protein and determine the protein product size (and amino acid sequence where protein sequencing is available).

To get the upstream and downstream regions of your fragment you can use a technique called inverse PCR. This involves digesting the chromosomal DNA then self-ligating the pieces so that they form circles. Then use the complements of the sequences that you would have used to amplify the DNA fragment to amplify the DNA in the other direction (i.e. upstream and downstream). This technique works. You can see an example of how we used it in the following reference: Microb Ecol 57: 423-436 (2009).

I also would recommend to use degenerated primers designed on homologous DNA sequences. Even if you manage to clone only a fragment of the gene of interest you can complete your sequence by 5' and 3' RACE.

First of all you can find out the closest type strain from the 16S rDNA seq and check for the cellobiohydrolase activity in that type strain. If that strain shows cellobiohydrolase activity then you can check the corresponding gene for this activity in that type strain.